Help me kill my alternator - it is stubborn and won't die

[Daox]

For the past few days I have been attempting to do an alternator disable on my 2014 Mitsubishi Mirage. I'm going to do it electrically, not unbelting, or removing the alternator. I've done this on several vehicles, but this one is proving to be a bit of a challenge!

Here is the system description of how it works, and diagrams to go along with it for reference.







My first thought was to cut and put a switch on the FR (field regulator) wire. I did this and it did stop it from charging... kinda. As soon as the engine revved up too high, it would start charging (self exciting I am guessing).

So, version two. I figured that killing the S (sense) wire would do it. However, I couldn't be more wrong. Instead of defaulting to not charging at all, the alternator blasts on at 15V.

I am thinking that my next step will be to install a dc-dc converter that takes 12V and converts it to 15V. I will send this 15V signal to the sense wire when I want the alternator to turn off, and let it see normal battery voltage when I want it turned on. The service manual specifically says (see above):

When the battery voltage (generator "S" terminal voltage) reaches a regulated voltage of approximately 14.4V, the field current is cut off.

So, I am hoping that 15V will do it. I have already ordered a tiny $3 dc-dc converter to do this job.

However, if you see a simpler way to do this, I am all ears!

[Daox]

Just thinking now... if I cut the G wire, the regulator won't have any ground reference unless its grounded to the alternator casing (which is quite possible). So, I wonder if cutting that wire would do it?

[redpoint5]

My Acura has a 4-wire harness going to the alternator. I don't remember what all those wires do now, but I do recall I had to disconnect all of them to kill the alt. Have you tried unplugging all of the control/sense wires to the alt?

I bought a 4 circuit switch and used wire harness from Ebay (so I don't have to slice my original harness) for the purpose of wiring in the dash switch, but never got around to it.

[19bonestock88]

Why not make an extra, 14.4V battery pack to boost system voltage to where the alt doesn’t charge? Like the guy with the virtual alt delete? Would save you the cutting and splicing...

[Daox]

Thanks Redpoint. Mine is also a 4 wire as you can see. I may try the ground next before my dc-dc converters get here.

19bonestock88, the 14.4V pack is a great idea. It would definitely work nicer than just the alt delete. However, I'm really not looking to spend on a pricey lithium battery at this time.

[California98Civic]

Originally Posted by redpoint5

My Acura has a 4-wire harness going to the alternator. I don't remember what all those wires do now, but I do recall I had to disconnect all of them to kill the alt. Have you tried unplugging all of the control/sense wires to the alt?

I bought a 4 circuit switch and used wire harness from Ebay (so I don't have to slice my original harness) for the purpose of wiring in the dash switch, but never got around to it.

This is what I do with my Civic. I had the problems you had. I had to disable all wires into the alt or the unit did not entirely quit. One problem remained, however, once I turn the unit on from the dash, the only way to turn it back off is by cutting the engine. I decided to live with it because of how often I do EOC, but a better way is certainly available if I figure out how to draw off the extra power keeping the field windings charged.

[ratgreen]

A 4 pole double throw switch would probably be the easiest option, one switch to disconnect all 4 wires.

[Daox]

Originally Posted by California98Civic

This is what I do with my Civic. I had the problems you had. I had to disable all wires into the alt or the unit did not entirely quit. One problem remained, however, once I turn the unit on from the dash, the only way to turn it back off is by cutting the engine. I decided to live with it because of how often I do EOC, but a better way is certainly available if I figure out how to draw off the extra power keeping the field windings charged.

Great info. Thanks!

Yeah, its sounding more and more like the dc-dc converter route is the way I'll go then. I can just fake the signal to the voltage regulator and that should kill the power generation pretty effectively. I'd rather not cut a bunch of wires if I don't have to.

[California98Civic]

Originally Posted by Daox

... I'd rather not cut a bunch of wires if I don't have to.

Another way is to get an extra OEM connector and plug it into the alt on one and and your car's wire harness's connector on the other. That way you do not cut wires on your car's harness.

I like the DC/DC converter, tho. Smart, if slightly more costly.

[Daox]

I hope it works out. I just got the dc-dc converter in today. I should be able to get it installed this weekend. Its just a very tiny chip based converter, it can only handle 1W of load. But, it should work great for this signal level stuff. I tested the sense wire on my alternator and it pulled 1mA.

I am also hoping to add a few transistors in as switches so I can enable the alternator on demand for some regen braking capability.

However, first steps first. Today I just unplugged the connector on the alternator. Yep, that worked haha.