Civic alternator shut off, the easy way
 

Well I've spent hours testing today and i've confirmed and refuted some theories with the Honda alternator.

My test setup:
96 civic hatch, with 96 civic alternator on a 92 d15z1 engine. I think the obd1 civic alternators operate the same way as the obd2a civics, but I can't be certain as I didn't test it.

I had a basically dead car battery (so dead that it wouldn't run the fan or light up any lights) and hooked that up to the battery cables. I then used a known good working battery to jump start the car for the beginning of each test. As soon as the car started I disconnected the jumper cables to isolate the good battery from the bad one.

The car was brought up to operating temp.

Note: When its up to temp when you start the car, the engine doesn't rev over 2000rpm. This is an important thing to remember, because when you test the voltage at the field winding with the car off there is .01volts, when you start the car its .05-.3 volts. When you rev it past 2000rpm it now reads 3-5volts and even if you let the car idle, it will stay at 3-5 volts.

There are 5 wires at the alternator. 1 white "B" charging wire, 1 yellow/black "IG" field winding exciter wire, 1 white/green "C" charging control signal wire from the ecu, 1 white/blue "L" charging warning lamp wire, 1 white/red "FR" charging rate wire from the alternator to the ecu.

I disconnected these wires directly from the 4pin plug at the alternator for guaranteed results.

Don't try pulling the alternator fuse because the manual, says it controls the alternator, vss, eld unit, evap purge control oxygen sensors and tcm. That's for a 96 civic anyhow. Its much better to disconnect the "IG" wire at the alternator.

TESTS:

1. First test was unplugging all 4 wires together. The car immediately died after disconnecting the jumper cables, but wait..... If you rev the engine past 2000rpm before disconnecting the jumper cables, the car would run very poorly. headlights would flash, the fan would pulse, it is a not drivable but actually charging at a super small amount.

2. Disconnect all 4 wires, but ground the "C" wire, The car immediately died like in 1, but if you revved it past 2000rpm before removal of the jumper cables the car idled, but was more rough than in 1. This is because grounding the "C" wire tells the alternator to charge at the lower rate.

3. It has been thought you can simply disconnect the "IG" wire and disable the alternator. This resulted in charging the battery and providing enough power for lights, fan stereo, ect. The car idled just like normal and you could drive the car just fine. This didn't work.

4. Another ecomodder California98Civic http://ecomodder.com/forum/showthrea...8-a-20513.html told me that he found out that if you disconnect the "IG" and the "L" wire this disables the alternator. He thought that the "L" circuit was providing enough power to energize the field windings. Well he was right. I tested this by starting the car with both "IG" and "L" disconnected and it operated just like test 1. I also tried starting the car with just "IG" disconnected, removed jumper cables, the car ran fine, then disconnected "L" on the fly, the car imediately starting running super rough like test 1.

5. I read that if you soft ground the "IG" wire via a light bulb this will disable the alternator. With just soft grounding "IG" the results were the same as test 3.

6. With disconnecting "L" and soft grounding "IG" i got better running characteristics and presumably better charging than in test 1. (I can't remember if it was like normal running, or just smoother test 1 running, sorry. This isn't a good option anyway.

People should either do 1, 2 or 4. 1 and 4 are almost the same, except with 4, the "C" wire is still connected to ecu. I feel however that 2 is the best.

So what did I end up doing? Well you can disconnect the "L" wire anywhere between the alternator and the ELD. So for ease of turning back to stock i simply took the charging bulb out of the dash and got the same results as if you disconnected it at the alternator.

I also used a dpdt switch in the UP SETTING to switch "C" to ground, and simultaneously switch off the "IG" wire. This is the same as test 2. Except that the bulb is out instead of the wire at the alternator for the "L" wire.

In the DOWN SETTING the dpdt switch will reconnect the "C" and "IG" wire to their normal connections, allowing full use of the alternator in normal configuration. The only thing is that you will never see a charging problem because you took the bulb out; however, if you use a voltmeter to monitor the battery as most would be doing, you will notice when something isn't right. We don't need no dumby lights.

This DPDT switch also has an OFF setting in the middle. In OFF mode, you get the same results as test 1 except that the "FR" wire is still connected. I didn't notice any differences in any of the tests with or without "FR" connected.

So how did the MPG compare?? I picked out a flat 35mph road and picked out 2 mailboxes 1 mile apart. Car was up to temp, car was already cruising at 40mph before I got to the first marker to eliminate variation with acceleration up to 40mph. Once I passed the marker I reset mpguino to calculate just the mile long MPG. I read what mpguino said at the mile marker and then slowed down after.

I calculated from A-B and B-A, I tested with high beams on, fan on full blast, A/C off, and rear defroster on. I did the alternator on tests with a fully charged battery first to eliminate any extra load from trying to charge up a low battery from the other 2 test types. This was a high load test, i didn't have time to also test no load, but plan to do that sometime this week.

Results A-B Full load:
Alternator On normal: 70.7, 68.8, 68.1 = 69.2 average
Alternator Test 2 setup: 73.4, 76.7, 73.6 = 74.5 average
Alternator all 5 wires disconnected: 74.9, 74.2, 74.5 = 74.5 average

Results B-A Full load:
Alternator On normal: 62.8, 61.5, 62.2 = 62.16 average
Alternator Test 2 setup: 68.7, 69.7, 69.8 = 69.4 average
Alternator all 5 wires disconnected: 69.2, 68.8, 69.0 = 69.0 average

Alternator test 2 setup and completely disconnected (except belt) resulted in almost identical results. I truly think that test 2 setup hardly provides much charge, and thus puts very little mechanical load on the engine.

In the A-B test i saw a 7.65% gain in mpg, and B-A was a 11.6% gain.

I'm going to post these results on the first post of the thread as well.

These are my original results, but it appears that the alternator was still charging just in low mode.

***UPDATE*** It is thought that this method just puts the alternator into a 12.5volt charging mode. I will try to test this further and report back with results. Don't be convinced yet that this is fool proof.

This is a half how to, half my results from testing this mod thread.

I have a 96 civic hatch and swapped a d15z1 into it. After reading about people disconnecting their alternator I decided to give it a try. if you go to pdftown you can download the service manual for your honda. From this site Timely Topics -- Your Vigor's Charging System The diagram they use is almost if not identical to my civic's diagram in the manual. I learned the alternator charging control wire which is green/white for 96 civic) and sends reference voltage from the alternator to the ecu. If the ecu grounds this wire, the alternator stops charging. Also, with this method the charging light indicator on the gauge cluster still works. You don't have to get out of the car and use a huge 100amp switch or relay on the charging wire like some people have done. You also don't have to run wires through the firewall. The alternator charging control wire for my car goes straight from the alternator to the ecu. i tested this with an ohm-meter. I simply cut the wire about a foot from the ecu and ran extensions from both of these ends to my switch mounted next to the steering wheel.

I used a dpdt switch from radio shack to connect the alternator charging control wire to the ecu and also to ground (they didn't have a spdt switch or I could have just used one of those). Now I can switch it to normal operation or "off via grounding" on the fly. (See http://en.wikipedia.org/wiki/Switch for info if you don't understand what dpdt/spdt switches are)

The switch works and the voltage drops right away. I’ll post pics in a day or so.

By the way if you use a similar switch, the middle part is “off” and nothing is connected. When you do this the alternator is still charging because it doesn’t see ground on that wire; however, if you read that whole page on the acuravigorclub website if says the ecu uses the ELD and the FR signal from the alternator along with other engine sensors to control the idle. Well when I set it to off it was still at 14.7volts at the battery; however, the idle speed dropped like 200 rpm. But when the wire was grounded it was 12.7volts but the idle was the same as if the wire was still connected to the the ecu. ODD....

Here are my results of a ½mile test with no electronics on except radio, 40mph steady speed, 54degrees outside, car weighs 2460 with driver and full tank, used mpguino and got car up to test speed and reset the mpguino trip odometer at the same sign and checked at the same sign.

73.8mpg - alternator on
74.8mpg - alternator off - 1.355% better

Same tests were run but this time with headlights on, A/C on full, rear defrost on.

56.1mpg - alternator on
63.45mpg - alternator off - 13.101% better

The first test was interesting because the difference in mpg was so small that a variation on my driving could have caused the difference, also I should have had my multi-meter connected to the battery so i could see if the alternator was even charging. I will probably re-test this sometime soon.

The 2nd test appears to corroborate the results of other people. Though I understand this was only a 1/2mile test it was more of a proof of concept for me and my car.

Next i tried some highway testing. Same limited electrical load and full electrical loads as before, 30minutes after first 2 tests. Car was brought up to 65mph on the speedometer (62.5 on mpguino) and i drove a 2.5mile course from A-B and then B-A and recorded results.

A trips (more downhill than B trips on same highway stretch)
56.6mpg - 62.7mph average - no load, alternator on
57.21mpg - 62.8mph average - no load, alternator off - 1.077% better
48.2mpg - 62.66mph average - with load, alternator on
50.14mpg - 62.90mph average - with load, alternator off - 4.024% better

B trips (lots of uphill, and my car is heavier and less aerodynamic than the civic VX from which the motor came from and thus it drops out of lean burn more easily than I would like, especially on hilly terrain at speed)
38.8mpg - 62.4mph average - no load, alternator on
39.7mpg - 62.5mph average - no load, alternator off - 2.319% better
38.3mpg - 62.5mph average - with load, alternator on
39.7mpg - 62.4mph average - with load, alternator off - 3.655% better

Here are some of my thoughts on the results.
1. With alternator off there was always a gain in mpg. I think this would carry over to full tank results as well.

2. with my vehicle the short run highway testing resulted in only a best of
4% better. I would like to do some long range highway tests to see if there is more of a gain or not.

3. The short run testing with load results was amazing, and with test results like this I ‘m curious if there was a fluke. More short run testing needs to be conducted to verify this. My car gets awesome gas mileage at 40-50mph, and I should re-conduct these tests without A/C, but instead just max blower on, as the A/C sucks a lot of power from the motor.

4. Though with no load my results at low speed were similar, I have to feel that over time and distance the battery will need to be recharged more (obviously) and when it needs this the alternator will kick in and then the MPG difference will be relevant again.

5. If a lot of my driving will be in town then this mod might be worth doing depending on charger/battery cost, cost of fuel, charging cost(120volt from house), and years for payback.

6. As for my initial highway results, it would not be worth the amount of effort or cost (for me). Though I agree that every little bit helps, the inconvenience of having to plug the car in to charge the battery, the cost of battery, the risk of being stranded due to user error, possible decrease in battery life, ect would not be worth a sub 5% increase to me.

7. I don’t pulse and glide or engine off coast, I don’t know by what amount that would change the percentages, but for these tests i was concentrating on staying at a steady mph, and less on feeling the gas pedal and trying to maintain MPG by slowing down up hills or accelerating in anticipation of hills like I normally do. A few 30-100 mile trips need to be conducted for me to determine if I should or shouldn’t persue this long term.

8. I would like to test the results with the alternator turned off against taking the alternator belt completely off to see how much actual drag there is. Lots of people say "its hardly any drag", but I havn't seen any actual back to back, ABA testing.

9. I did some in gear coast-downs and while getting 999999mpg doing so I switched from alternator on to off and you could feel the car slowing down faster with it on than off, so i know the switch was working. Also, i tried a few full throttle in 2nd gear tests getting up to highway speed and when you switched the alternator off it was like a subtle "vtec kicking in", you actually got a boost in acceleration. It was fun to flip it on and off several times on the same acceleration run to feel the car bog, then accelerate with the switch. By "bog" i mean you could feel the drag, it wasn't a ton, but was definitely noticeable.

Hopefully this information helps some guys. if you have any questions feel free to ask, I hope i can help.

This first picture is my mess of wiring for my obd1engine to obd2acar conversion.
http://img192.imageshack.us/img192/3876/ecuwires.jpg

This one is of me holding the green/white alternator control wire from the engine harness.
http://img12.imageshack.us/img12/8961/correctpin.jpg

I taped the lead to the middle wire to test for continuity to the alternator plug.
http://img715.imageshack.us/img715/6...wireforohm.jpg

Picture of the ohms while testing.
http://img190.imageshack.us/img190/6264/ohms.jpg

Picture of what pin on the alternator plug is the alternator control wire.
http://img194.imageshack.us/img194/4...seupofplug.jpg

This picture is with the alternator switch in the up position to run as normal.
http://img252.imageshack.us/img252/7605/alton.jpg

This is when you switch to the down position to ground the alternator control wire.
http://img69.imageshack.us/img69/3023/altoff.jpg

I've been playing around with this too. Does the alternator actually shut off? I got the impression from my service manual that it just reduces the charging voltage to 12.5v. In other words, the battery won't be drained by running at the 12.5v mode for extended periods. I know the voltage drops fast during engine off coasting with the headlights on. I can run a lot of accessories with the 12.5v mode and the voltage seems to stay there.

I have a voltmeter in my Civic and grounding the control wire does drop it to 12.5v from 14.5v. But not always. Sometimes the alt doesn't respond and sometimes it will drop to 12.5v and then eventually jump back up to 14.5v. Have you seen anything like that or is my alternator just weird? Or does the alt have the ability to override the control wire signal?

steffen707,
Excellent report, many thanks, you're a champion.
I have been pondering this for a while with my vehicle, so through all you're testing no warning or alternater lights, that's great.
It looks like you have confirmed a positive gain of 2-3% if this was used constructively, i.e. on downhills and other times when brakes are required, this could come out as an overall gain of 1%, although it doesn't seem like much add a few of these types of adjustments together and the $'s start to add up, or as I am thinking add say a 50w solar panel to the system and there may be no need for alternator or home plug in 90% of the time.
Good work, look forward to hearing more of your progress.

You raise a thought that I have also had. Compared to modified driving, like P&G, savings like these are so small you really have to wonder if it is worth the trouble...

UGH! I didn't have my voltmeter hooked up while trying all the tests. I was too lazy to find a positive and ground and tap into them, but it looks like I need to confirm or deny your results that the alternator will still flip to 14.5 volts. I was really hoping that my results were good and that it fixed this troubling problem for civic owners.


You could be right about this. How would I go about checking to see if the alternator is actually off, and not just charging at the low setting? This is frustrating but I like to try and be thourough. I suppose I could try my tests again and just unplug the 4pin plug and main charging wire from the alternator between tests.

Thanks Tesla, as others have pointed out, this might not actually be working as efficiently as a true alternator shut off should be. I will have to do more testing and report back before we go jumping for joy. :)

Do you guys think if I disconnected the alternator charge wire from the battery, put a big fuse between the battery negative terminal and connect that to a light, and then connect that to the alternator, that would let me know if the alternator is actually charging or not?

Another factor as the voltage drops is that the ECU adjusts the fuel injector timing to compensate. This may affect efficiency and also the calibration for Scangauge or similar systems. I tried to find out once if Scangauge did calculate fuel correctly based on injector timing. I think it may do so but I'm not 100% sure.

Since you are dealing with rather small differences here, you may have to perform a dedicated experiment to quantify these effects. If your instrumentation calculates correctly when the ECU/injectors run on low voltage, it gets easier. Then you only need to find out if the engine works better or worse with normal/low voltage. If there is a degradation, you may be able to find a workaround, eg. extra batteries to keep voltage up.

At least some of your test runs indicate that your engine may degrade with lower voltage.

Well I don't use scanguage because the d15z1 and civic VX are obd1, so i'm using mpguino.

I would have to do long term testing if what you think might happen is true, that the injectors fire slower, or the ecu compensates on the injector pulse width.

I don't see how my test results indicated degradation though, because in every test I got better gas mileage with the alternator off.

Check out this thread: http://ecomodder.com/forum/showthrea...8-a-20513.html

This probably has something to do with why your alternator is not completely shutting off. Here is the important part:

Thanks for the link, that's also a good read, but I was hoping that the grounding method would provide a more simple way to achieve alternator shut off than having to disable 2 wires, also i've heard from some ecomodders that have done the 2 wire shutoff as described in your link and that didn't work either.

We don't know for sure yet if the grounding of the alternator control wire still charges but at a lower 12.5volt rate, or if its actually working.

Any good ideas to test the alternator output to verify if it is still charging but at a lower rate? Would that light bulb between the alternator and battery ground work like I suggested trying?

Good luck with the further tests! Please report more on your findings. Nothing cooler than testing something and being willing to admit if the test has failed, if it has failed.

And I like the FE results you are suggesting (which confirm my similarly sketchy results). It would be nice to know if the alt really was off.

One observation: your design is simpler than the one I posted, and that cbaber linked above. But the only extra thing I did was unplug the charging light wire near the driver's side firewall grommet, right? That's reversible in 30 seconds.

I know brucepick has had difficulty with the method I describe in the linked post, but he is not sure yet what the source of the failure is. I haven't seen any others mentioning problems. Who are you referring to?

I have a voltmeter on my dash, and for what it's worth to anyone: in 7 months my alternator has not once begun charging unless I turned it on. If I drain the battery below 12.5 volts or if electrical load brings the voltage down below 12.5, it stays there, the alt does not turn on unless I flip the dash-mounted switch. Quite handy, really.

Thanks again,
james

Europe and Canada do not have ELD.
I have 14.2 ish volt on battery on idle all the time.
So I gather I cant lower mine to 12.5, that sucks.

I was also referring to brucepick's problems.

When you said that it won't drop below 12.5 volts, do you mean that you physically don't let it drop below 12.5 volts because you use your dash mounted switch to turn it back on?

Or are you saying that with your kill switch the alternator is always off and just doesn't fall below 12.5volts? Because if the later is the case, it would make me think that the alternator is stuck in this 12.5 volt "low setting" that Gasoline Fumes says mine might be in.

Neither. An example: today doing P&G with EOC on my way to work, in the cold, with the alternator off, the voltage would get down to 12.3 during the pulse phase and stay thereabouts for the whole pulse length, whether 5 seconds or an entire minute. Then during the EOC glide phase, with decreased load from the ignition system, the voltage would return to 12.6 or 12.7, which is near full charge. With my previous battery, which did not have as much capacity, I would drive for miles without seeing the voltage return to 12.5, whether the engine was off or on. But it is true that this design will not accomplish your desire to be able to cut the alt off and have it shut down, without cutting the engine for at least a second, as I do with my injector cut-off. I think drmiller's idea of a small light bulb on the line to drain residual voltage might be another way to accomplish your goal. I just didn't need it because my car is off so much of the time, so often, while I drive.

I have not had the alternator on for days now. It's all grid charging.

I just loaded a bunch of pictures to post 2 of the thread.

I think the alternator's reduced-charging mode is actually a not-charging mode.

A lead acid battery has a "resting" voltage of 12.5V. It will usually settle there if there's no load, or a very low load, like just the computer + maybe the radio running. With alt not charging, it will then gradually drop over a minute or two. A deep cycle battery drops much more slowly. Once the battery voltage has dropped to whatever the ELD circuit's low voltage limit is, the ELD reactivates the alternator to charge the battery.

So I suspect the ELD circuit cuts the alt's output, and the car "coasts" on the existing charge in the battery. In normal use (not with an alt delete mod done to the car) the ELD only cuts the alt output intermittently, so in between those outages the battery is getting topped up.

Non-charging mode is only available if these conditions are met (I tested and watched carefully):
Speed below 50 mph
Headlights off
Battery topped up
Heavy consumption accessories not running (example, fan on speed one is OK, but not speed 3-4)
Car NOT coasting in gear (ELD is programmed to take advantage of the "free" energy of the coast, and will use it to charge the battery)


So in normal driving, it will cycle in and out of not-charging mode as conditions change. Battery is slightly depleted after startup, and the alt charges normally till it's topped up. The ELD circuit can sense the current "drain" presented to the alt by the slightly depleted battery that powered the computer + clock all night, and then started the car.

When hypermiling, with EOC and DFCO and whatever other methods, not-charging mode will also cycle on and off based on the same requirements.

So you're saying that by grounding the alternator charging control wire (like the ecu does when it wants to go into "low or no charging mode") that its actually NOT charging?

If I read correctly the ELD tells the ecu what's going on and the ecu controls the alternator by just the alternator charging control wire. So the ELD isn't connected to the alternator directly.

When you just ground the alternator charging control wire, the alternator shouldn't have any idea what the ELD is.

One complication for this picture is that I observed 12.5 volts charging on my old battery--the dieing one--under certain conditions. In other words the battery was sitting at say 12.2 volts and I turn the alt on and the voltage goes to 12.5 or thereabouts.

If you start your car, use your switch to "shut off the alternator" and then yank the negative battery terminal cable off, that should shut the car off unless the alternator is still charging right?

Never remove a battery terminal with the engine running. Unless you want to permanently disable the alternator.
Don't Disconnect the Battery with the Engine Running

I'm pretty sure the low output mode is still charging. I can drive as far as I want without losing any voltage. Honda says 12.5v, but my multimeter tells me it's more like 13v. The easy test to see if it's charging or not is to force the alt in the "low" mode and drive with all the electrical accessories on while watching an accurate multimeter. If the voltage remains steady, the alt is charging. This is what I'm seeing in my '91 Civic.

HOLY CRAP! Thanks for the link and glad I didn't try that before reading this. Guess I'll try another way to test if the alternator is still charging.

I went and bought a volt meter that plugs into the cigarette lighter port. I've been driving the car for several days now with my switch to ground. The battery is now showing only 12.2 volts.

I started the car and it was at about 12.3 volts while running and no extra load.

I then shut the car off and unplugged the 4 pin connector from the alternator. Started the car again, and it was showing only 11.6 volts.

Looks like my easy method doesn't disable the alternator, just puts it into low charge mode. The results aren't all bad, considering I saw a 3-4% gain on the highway while still charging. i wonder what it would be with the alternator completely disabled.

steffen707,
If you need a heavy-cable alt cutoff switch,

The 300A cutoff switch I use to disconnect the alt from the battery cost $8 at a battery store. I've seen them at Walmart for $5ish but there's no AH rating stated on those.

The purple wire goes directly to the alt's positive terminal.

http://i188.photobucket.com/albums/z...tchCloseup.jpg

You'll also need to do these for this application:

1. File or grind out the interior some, to accommodate the larger + battery post. They're made for - posts which have a smaller diameter. I tried just spreading the ends of the circle but the other end of the circle doesn't widen.
   
2. Get a nylon bushing about 1/8 inch thick from the fasteners section in a hardware store. Use it between the knob and the switch body. With the switch mostly "OFF" for alt-less driving I'm concerned the screw would vibrate loose if you leave it there, and worse, two metal plates may then separate from vibration. With the nylon bushing in between you can tighten it and keep the switch "OFF".
   
3. Run a dedicated alt cable directly to the battery. Purple wire in photo above; oem cable and new connector in pic below. Disconnect the original that goes to starter and tape the end over. See this post for some notes re. the pic below.

http://i188.photobucket.com/albums/z...onnectors2.jpg

You can probably use a nylon locking nut that would stop it from vibrating loose. After testing my ground switch and finding that its still charging a little but survived several days, i'm thinking of just running a 4 wire switch all the way from the alternator to the car and back to the alternator. Shut off all 4 wires and start the car. Then the alternator will be off. If you already have the car running, just switch the car off at the ignition key or use your fuel injector cutoff switch to kill the motor, turn the 4 wire switch off, and then bump start the car.

Also, I think if the alternator is off and the engine running and you want to start the alternator again, just flip the switch and it should start working on the fly. You would only need to do this when you're on a long trip with the alternator off and monitoring battery voltage you see the battery is getting too low, just flip the alternator back on and it will charge up the batt for you to safely get to your destination and then plug in your on board charger.

I've got Sunday off so i might report back on this then, otherwise I might be able to work on it tonight as the fiance works till midnight.

I went to the junk yard and cut off an alternator 4pin plug, i'm going to make a jumper harness for a nice factory look.

Hey Brucepick, do you only use the big power switch to shut off the alternator? Or do you also do something with the 4pin alternator connector?

I do leave the 4 pin connector unplugged when not running the alt, but of course the positive output cable being switched off absolutely prevents charging.

As for the 4 pin, I think that if not charging, it makes no sense to send those signals and voltages across the small wires, so I pull that one too. Once or twice I forgot to pull the 4 pin; no serious consequences but I think there's some load in leaving those little circuits operating.

I only plug in the 4-pin part way when I do use the alt (which is rarely). That way it's easier to unplug again later. Getting at the release can be a pain. Access is definitely improved with a replacement direct alt charging cable that approaches the alt from above as opposed to the oem which comes up from below.

I'm definitely interested in seeing the results of your testing if you're able to get time for it.

I also got a couple junkyard 4 pin plugs but found the area so cramped I was never able to insert my own wiring magic between the alt and the existing 4 pin connector. It should be somewhat easier if you disconnect [and tape over] the original alt charging cable at the alt and run one direct from the battery, approaching the alt from above. Be careful of that cable, it's hot. Really you need to disconnect the ground before you mess with it; I had a loud spark.

Remember that having the alt charge up a battery that's pretty well discharged works to defeat the purpose of the alt delete mod. This is especially true because the alt's mechanical load, as seen by the engine, is somehow proportional to the amount of charging it has to do. A depleted battery will present a higher amps load to the alternator which will be a bigger drain on your fuel.

I got out of that by using two batteries. The deep cycle COULD be charged or maintained by the alt but I don't use it that way. The regular starting battery is in place. It's wired to the starter so it does that job. The deep cycle battery does everything else.

I'll use the car in it's original configuration if I need to do a long road trip, or say I've already driven the limit of what the deep cycle can handle and now I need to run headlights for a half hour or so, which the deep cycle can't do after being mostly depleted. So I'll switch the alt back on and reconnect the 4 pin, and I'll flip a couple other switches to run the entire car off the alt + starter battery. The deep cycle goes "out to lunch" until I'm able to charge it up properly from wall current.

Well I never thought about doing that, but great idea.

That way when the deep cycles are depleated you flip it over to regular starting battery and the alternator doesn't see the huge load of the depleated deep cycles. I got it! :)

Did you ever find the female side of the alternator plug? I guess I don't know which one is considered the male end and which the female. I was hoping i could find the other end somewhere, but without tearing apart an alternator housing i don't know if this path is possible.

Thanks! :D

I never did find the other side of the alt connector. I asked a few people and in parts stores and even an auto electric shop. No go. I tried using 1/8" wide male blade crimp connectors. You need to narrow them some otherwise they don't want to go into the metric-dimensioned slots in the cables' side of the connector. I used a Dremel for that, with a (fiber-reinforced) cutoff wheel. One of my absolute favorite tools, sorry I didn't get one years earlier.

Anyway, the narrowed blade connectors do the job but access is horrible until you remove the alt + cable. I gave up on the idea and did my thing with a new alt cable and the green knob switch. With that, I didn't need to build switched wiring between the separated 4 pin connectors.

Even with the positive cable out of the way, it's kinda cramped there, but you might be able to make your connections. Just be sure you pull the battery ground cable before you go near the alt + cable.

I actually don't have that hard of a time getting at it. I might have a smaller brake master cylinder or something. I've got smaller hands as well. Also when I had to completely modify the engine harness I seperated the alternator wiring from most of the engine harness and re-loomed it back over by the starter to the rest of the wires, so my main alternator charging wire isn't in the way of the green plug.

I de-pined the green alternator plug last night to see what kind of connections they are. Kinda look like ECU pins.

I think what i'm going to do is buy two 4pin plugs, cut off the old plug and solder/heat shrink the wires to the new 4 pin male plug, then make a female plug that goes to the switch, then back from the switch to another 4 pin male plug that plugs into another female plug that's soldered and heat shrink tubed to my new alternator plug.

Kinda confusing, but if you follow, I can unplug the switch alltogether and just plug the male end of the wires to the female end connector and go right back into the alternator for a back to stock configuration.

Disapointing update guys:

I went out and performed a bunch of tests with the alternator on, with it in low mode, and then I shut the car off, pulled the 4 pin plug from the alternator, started up the car to do an alternator off test and my volt meter was reading 14volts..WTF!? HOW IS THIS POSSIBLE.

So I remembered a thread where people said you need to soft ground the yellow/black wire from the alternator because the field has residual charge in it, even if you shut the car off.

I noticed when you first start the car it isn't at 14 volts, but as soon as you rev it past 2000rpm it starts charging. Also it goes up to 14 volts and then stays there until you shut the car off.

I tested the voltage from the alternator yellow/black wire to ground, it read .01volts. I disconnect the main charging wire at the fuse box, the alternator yellow/black wire now reads 0, put the charging cable back on it reads .01 again.

Keep in mind I don't have the 4 pin plug connected to the car, its completely severed, I cut all 4 wires and am just testing voltage coming from the alternator to the yellow/black wire.

I fire up the car, test the voltage and its somewhere around .05-.3 volts, it likes to skip around, as soon as you rev past 2000rpm it goes to 3-5 volts and stays there.

So now i'm thinking, okay the main charging wire is supplying this voltage to the alternator somehow, so just disconnect the main charging wire, right?!! WRONG.

I disconnect the main charging wire at the fuse box, tape the wire off and isolate it from touching anything. Car is off, check the yellow/black wire, 0 volts, start the car, it reads .05-.3 volts again. Rev it up past 2000rpm and it reads 3-5 volts.

So now i'm clueless. Even if you disconnect the 4 pin plug and disconnect the main charging wire from the alternator to battery, that stupid yellow/black wire still gets electricity and i'm guessing that its still forcing the alternator to charge, even though the electricity isn't going anywhere because you disconnected the main charging wire.

The only way i can think of testing this is to do some MPG tests with the alternator belt off, and then with the belt on but disconnect the wires to the alternator. Compare those 2 results and see if it is in fact charging.

Back to that soft grounding of the field wire to discharge any electricity that's being generated. I tried the light bulb trick, but it didn't stop the alternator from charging, it did lower the volt output from say 14.2volts to 13.6, and when you would take the bulb off ground, it would shoot back up to 14.2 volts at the battery.

Do I need a bigger bulb or instead a resister to drain all this power? I'm afraid to play around with it, for fear of burning up some components in the alternator, and then i'm SOL. I used a test probe bulb, and also a light bulb from one of my craftsman work lights.

So frustrated........

Steffen707,

Good testing. Thanks for doing all that and writing it up.

Re. your note below - -

Please google "Single wire alternator" or take a look at this Summit Racing results page. Only one wire is needed for an alternator. One.

You have to remember that the mechanical load of an alternator (or generator) is basically proportional to the amount of power being use at the alternator's output. If there's zero output, the alt's mechanical load on the engine will be very low indeed, just bearings and belt flex resistance etc. Now, for two examples of the same alternator, running at the same (say) 3000 rpm. One running a little cluster illumination bulb, the other running headlights plus a bank of off-road illumination bulbs plus a monster stereo. The fuel needed to run the first alt will be a lot less than the fuel needed to run the second one.

What allows the alt to get going?? I'm still convinced it's just a property of spinning magnets and stationary wire coils. Spinning fast enough and long enough, the system will set up a magnetic field and eventually will start outputting some voltage. The yellow-black wire is just an "exciter" wire, to get that going immediately. That's all.

So are you saying that if you disconnect the alternator output from the battery, the alternator will see no electircal load, and therefor exert little to no mechanical load on the engine?

Is it safe (for the alternator) to have the alternator output wire disconnected as long as it doesn't touch anything to cause a fire or short circuit?

I'm sure of it, on both points. I'd do a pretty thorough job of taping protecting the disconnected end of the alt's original + output wire, as the other end is connected directly to the battery + wire, at the starter motor.

I also keep the alt's 4-pin connector detached from the alt. I do that because

1. We're pretty sure it delivers some signals from the computer to the alt. With the alt disabled, that current now comes from our deep cycle battery, which we want to discharge as slowly as possible. (and)
   
2. We haven't completely figured out how that circuit works but its certainly possible that at least SOME of those wires deliver current from alt to computer. So that power will have to be generated by the alt, or possibly by the deep cycle battery, and we don't want either to be happening; it's a waste of the energy we're trying to conserve.

All that work just disable the alternator why not just put a toggle switch on the fuse #15 witch is ALT fuse when blown alternator wont charge at all

Because cutting Fuse 15 kills several functions, not just the alternator.

What functions are they I thought that was just for alternator

Speed sensor is one; that's visibly fed by the same fuse when you view the circuit diagram.

When I tested pulling that fuse I got a check engine light while the fuse was pulled. Stayed lit while I idled the engine for several minutes. CEL went away after I shut down engine, replaced the fuse and then restarted engine.

"All that work" is relatively little work when doing it.