How to Install an alternator cut-off ("kill") switch on a 1998 Honda Civic

[steffen707]

Originally Posted by California98Civic

I have a dash mounted volt meter. Unplugging the 4P plug will always keep the alt completely off. It cannot power-up itself through the thick white charging wire to the battery. My switch disables two of the wires in the 4P connector. If the alt is running and I cut the switch, the alt still charges until I cut the injectors and bump start again. But according to some, a small light on the line can drain the residual charge in the field windings (I have not tried this).



You might try taking the powr steering belt off as a test of this idea. It's easier than an alt disable and completely reversible.



I believe the answer might be yes, because the alt will be generating power with nowhere to go. But why would you want this? The power generation itself would still be a parasitic draw on your engine.

I hope those answers help.

My thought was that if you switch off all 4 wires and the main charging wire, so all 5 wires, then the alternator should shut off. I wanted to be able to do this on the fly so I don't have to go under the hood to reconnect anything, or bumpstart the car, even though bumpstarting isn't a huge pain.

My car doesn't have power steering.

So that's why people put the small light on the field winding wire, to drain the field windings of the electricity so it totally stops.

[stylus]

I have a 96 Tercel, I have not done any kind of alternator mod but I do have an idea of how long my car will run with a dead alternator. My commute to work is 15-18mi each way (depending on path). I can run my car back and forth at least 3-4 days before the battery is weak enough to cause a problem. It took me a few weeks to get it all straightened out becasue I got a defective replacement alt from the parts store and I didn't have time to swap it out again.

My problem with this type of mod is that Energy = Energy. If you are not charging your battery using the alt, and you charge it from the grid you are still paying for the energy on your electricity bill instead (likely at a "cheaper rate").

Also isn't a battery charger plugged in to a car battery for 8-10hrs at a time going to waste energy once the battery is "full". Kind of like people complaining about leaving cell phone chargers plugged in 24/7 even if they are not charging the phone.

Yes I can see that if you are able to maintain the battery with a solar panel you are ahead of the game.

[turbotomass]

From my understanding of the civic charging system and batteries/alternators is that, oh at one time I was really interested how the ELD system worked exactly I could be wrong, Is it more or less will turn off the alternator if the charge is below X (unkown to me) under 40mph and less than 10amp of electrical load.

I was thinking and someelse brought it up in a forum as to why the strategie wasn't used all the time, say at 60mph freeway speeds. I'd love to see the results of this system being utilized 100% of the time.

from being a mechanic I see how batteries act. if you do a deep charge, like say 20 or less amps for say 2 hours. when you come back to test you'll usually see something like 13. high 12 volts. surface charge. you could be using that to when cycling the alt. on and off.

another question or curiosity would be hooking up a voltmeter to see honda's strategy in action under 40 mph with no elec. loads on. or hooking up an amp clamp and seeing if with all loads off how much amps are being used. usually most cars I hook a VAT to are in the 15-20 amp range or more

[steffen707]

Originally Posted by stylus

I have a 96 Tercel, I have not done any kind of alternator mod but I do have an idea of how long my car will run with a dead alternator. My commute to work is 15-18mi each way (depending on path). I can run my car back and forth at least 3-4 days before the battery is weak enough to cause a problem. It took me a few weeks to get it all straightened out becasue I got a defective replacement alt from the parts store and I didn't have time to swap it out again.

My problem with this type of mod is that Energy = Energy. If you are not charging your battery using the alt, and you charge it from the grid you are still paying for the energy on your electricity bill instead (likely at a "cheaper rate").

Also isn't a battery charger plugged in to a car battery for 8-10hrs at a time going to waste energy once the battery is "full". Kind of like people complaining about leaving cell phone chargers plugged in 24/7 even if they are not charging the phone.

Yes I can see that if you are able to maintain the battery with a solar panel you are ahead of the game.

If you get a good charger it will go into "maintain mode" and only give short bursts of power to keep the battery topped up. I have one of those "killowatt" appliance testers that plug into your wall and then you plug your appliance into it. I can test what the drain over a few days will be for you, because I have an on board maintainer for my CRV as it sits outside in the cold most of winter, and I rarely drive it. The maintainer works flawlessly, and in the dead of winter i hop in, and it fires right up, so I know the maintainer does its job.

[somedude88]

Will this work with my four wire 1991 civic alternator?

[Randy]

The stock civic alternator has wire to turn the voltage down to 12v... basically shut off until needed, especially with a AGM battery which has a higher discharge voltage than a flooded.

Unfortunately I don't know which wire, but it goes to the ECU, and is grounded to shut off the alternator. You can just ground it with a switch to force shutoff (the ECU controls it with an open-collector circuit). I did this when I had a '94 civic. You can even monitor if the ECU has shut off the alternator by looking at the voltage: it's about 7 volts normally (you might need a 5k ohm load or so to see this), but about 0 volts when shut off. The ECU-controlled shutoff is fairly rare: it has to be warm, with no lights or fan on.

[steffen707]

Originally Posted by Randy

The stock civic alternator has wire to turn the voltage down to 12v... basically shut off until needed, especially with a AGM battery which has a higher discharge voltage than a flooded.

Unfortunately I don't know which wire, but it goes to the ECU, and is grounded to shut off the alternator. You can just ground it with a switch to force shutoff (the ECU controls it with an open-collector circuit). I did this when I had a '94 civic. You can even monitor if the ECU has shut off the alternator by looking at the voltage: it's about 7 volts normally (you might need a 5k ohm load or so to see this), but about 0 volts when shut off. The ECU-controlled shutoff is fairly rare: it has to be warm, with no lights or fan on.

As we have been discussing, this wire you're talking about is the alternator charging control wire. When grounded it doesn't shut off the alternator entirely. It still is charging, but at a very low rate.

[drmiller100]

from the peanut gallery, there are two wires which cause the alternator to charge, just like every other modern car.
the great big wire which goes to the battery and carries the juice, and a "trigger" wire, yellow/black which excites the field and kicks it off.

The rest are signal wires from the alternator back to the ECU which the ECU uses to keep track of how hard the alternator is working. For instance, at idle, if the driver turns the heater fan on high and rear defroster, there is more load on the alternator, so the ECU needs to QUICKLY give a touch more air to the idle so the engine doesn't slow down or die.

for your purposes, the signal wires are not really needed.

[California98Civic]

Originally Posted by drmiller100

there are two wires which cause the alternator to charge, just like every other modern car. the great big wire which goes to the battery and carries the juice, and a "trigger" wire, yellow/black which excites the field and kicks it off.

I basically agree, but remember that I have disabled only two of the signal wires, not the large gauge charging wire to the battery, and I can still completely cut-off the alternator. I put my switch in the off position and when I restart the engine with a "bump" or "roll" start, the alt is not on anymore. And it has never come back on in 7 months since unplugging the alt and the two or three months since completing the kill switch project that starts this thread.

I learned, using a process of elimination method you recommended, that if I disabled only the blk/yel and left the wht/blu connected (for the "battery" light on the dash) the alt would come back on. When I studied the wiring diagram it seemed the battery light was able to give just enough power to the alt to fire it up on its own. I'm not fully confident I am correct about that because it is not what seems logical in terms of design, but it is what experiment showed me, so I have followed it.

[steffen707]

Originally Posted by drmiller100

from the peanut gallery, there are two wires which cause the alternator to charge, just like every other modern car.
the great big wire which goes to the battery and carries the juice, and a "trigger" wire, yellow/black which excites the field and kicks it off.

The rest are signal wires from the alternator back to the ECU which the ECU uses to keep track of how hard the alternator is working. For instance, at idle, if the driver turns the heater fan on high and rear defroster, there is more load on the alternator, so the ECU needs to QUICKLY give a touch more air to the idle so the engine doesn't slow down or die.

for your purposes, the signal wires are not really needed.

While you are right, others have noticed that voltage can also come from the battery indicator light on the dash as well. I've also heard that if the car is running and you disconnect the yellow/black wire it will keep charging because the alternator already has the field charged up. Not sure on this cuz i havn't tested for myself. But i heard that if you ground the yellow/black wire from the alternator via a light bulb, it will slowly drain the field through the light bulb and then shut the alternator off.

While it sounds black and white, there's been several attempts and discoveries in this regard with mixed results. I'm simply trying many methods and reporting my discoveries so others don't have to.