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Old 08-29-2018, 01:57 PM   #1 (permalink)
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Help me kill my alternator - it is stubborn and won't die

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!

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Current project: Adding regenerative braking to the Mirage
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