Started my car last night to fill the coolant after doing my heads/cam swap and found that the alternator was pumping out 18V solid. Prior to doing the swap, it was fine, so I'm wondering if anything could have happened during the swap to make it act up. The only thing that was removed from it (the alt.) was the top wiring harness, the main battery cable was untouched. It may have had a bit of coolant spilled in it from water pump removal, but I don't think that could cause it to spike voltage like that. Any ideas?

 

Had the alternator tested, it's good - where should I look now?

 

Double check the exciter wire on the top (the single wire)...from my understanding, that wire is what the PCM uses to control the output voltage.

 

Yeah, that's the problem alright, but I can't figure out if it's the computer or the wire...

 

How far can you trace back the wire? Did it melt at some point, shorting out the circuit?

 

May have the culprit figured out... spilled a bit of coolant into the socket when I pulled the waterpump out. May have shorted between terminals in the alternator. We're putting it back together now to test it.

 

That's what it was... coolant in the socket.

 

Sweet...always a good feeling when you get something figured out.