Alternator not charging battery

More then likely this is the voltage regulator which is contained in the PCM.

The way to confirm this is to measure voltage on the dark green wire from the PCM. I suspect the regulator is not operating properly which is why your voltage is erratic.

Unfortunately if it were me, I would go with the PCM at this point.

Take a look at this info and we can go from there. Thanks

Hi,

As I believe you are aware, the alternator voltage is regulated by the powertrain control module (PCM). If you would have told me there were times that voltage dropped and then would return to normal, I would have first suspected a bad alternator or a connection issue. However, the spike in voltage (which can be dangerous) doesn't indicate an alt or connection issue. Instead, it indicates the PCM is not controlling the voltage from the alt at all times.

I hate to say it, but I feel the PCM needs replaced. Spikes in voltage as you mentioned can cause other issues including the potential for something to overheat and catch fire.

If you look at the attached pic, it is the entire charging system wiring schematic. Note where the voltage regulator is located.

Let me know if this helps or if you have other questions.

Take care,
Joe

Hi,

Honestly, I wouldn't recommend it on this vehicle. The idea of installing an external regulator is more for much older vehicles.

Have you checked online for better prices? The $300.00 sounds high.

Let me know.
Joe

Good call with not going with the external regulator. I have seen a number of people try this and it doesn't work out too well.

Thanks for the update. We will wait to hear back.