PCM question

[cumminsfreak86]

I am having a voltage regulator problem (flashing lights). Heres my situation, I have replaced the alternator and bought two new regulators to replace the old regulator which I believe was causing the battery to overcharge. Just on a hunch I completely unhooked the wire to the new regulator (essentially an open circuit) and did a voltage test. I then hooked up the new regulators and performed the same test. They put out the same exact voltage reading. I wonder how this is possible when the old regulator is causing the battery to overcharge? Because of this, I don't think it is a connectivity issue between the regulator and the battery.

I have a theory that the PCM has been replaced by a previous owner because the wiring does not look factory. My big question is:

Is it possible that the PCM that is currently in the truck can not communicate with the new regulators I bought for my 91.5 year model truck? In other words, if there is a PCM from a certain year model truck (say a 89-90 or 92-93) and I had a regulator for a 91.5 truck, would the PCM not be able to communicate properly with the new regulators I have now?

This is the only possibility I can think of. I am truly sorry for the book. I just wanted to make sure I provided adequate information.

Thanks,

Chris

[Ace]

Do you mean that with the engine running it makes around 14v with the external regulator connected or not?

[cumminsfreak86]

Yes, all my readings are taken with the engine running at idle. The new regulator makes 12.5 volts when hooked up. With the new regulator unhooked completely, I am reading 12.5 volts also. I read around 15 volts with the old regulator hooked up but that value fluctuates.

[Ace]

It should make more like 14v if it's charging.

[cumminsfreak86]

Yeah I thought so which is what gets me confused. I originally thought I just got a bad regulator the first time I tried to replace it because it wasn't charging. I then went and bought another regulator and the exact same thingtoo place. This is what led me the come up with the question/theory in my original post.

[cougar]

The regulator controls the field winding to ground. With the regulator disconnected, you should see only battery voltage. I would suspect a bad ground or connection to the regulator if the voltage is dropping. I would suspect the wire to the regulator is shorting to ground if the voltage was going up.

[cumminsfreak86]

Hmmm. I didn't think about that for some reason. I'll have to check it. Thanks man.

Chris