Civic alternator shut off, the easy way

[steffen707]

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?

[Gasoline Fumes]

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.

[steffen707]

Originally Posted by Gasoline Fumes

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.

[steffen707]

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.

[brucepick]

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.



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.

[steffen707]

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.

[steffen707]

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?

[brucepick]

Originally Posted by steffen707

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.

[brucepick]

Originally Posted by steffen707

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.

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.

[steffen707]

Originally Posted by brucepick

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.