Alternator Overvolting?

[rfiltz]

'92 MTX, Just replaced my alternator and began having weird problems with the ECC head unit cutting completely out at higher engine speds (around 3,000 rpm) and then coming back on when I slow down (around 2,500 rpm). Does this even in neutral. Thought I broke a wire and was getting intermiitent contact, but I think the voltage regulator in the new alternator is bad?

I get about 12.6 volts at the battery with the engine off. Battery was tested and is good. Engine at idle speeds I get about 14.5 volts, however as I increase rpm the voltage keeps climbing and got up to 18.5 volts at 4,000 rpm. Didn't want to go higher in neutral.

Is this a sign of a bad voltage regulator or alternator?

 

[SHOZ123]

Definately a bad regulator.

 

[SmyleySho]

Agree, max should be 14.5 at idle or acceleration

 

[AutoSHO]

Definately a bad voltage regulator, which is internal (in the alternator). Take it back and get another.

 

[rfiltz]

Took it back, new one seems to be stable. Have to road test the ECC though. That thing's a real pain to get at. Just wish I could get them to pay for my time re-installing!

 

[NotSoSlowSHO]

I had similar issue a few weeks ago. But on an alternator that Ive had for a while that was working correctly. Volt meter was showing irregular readings, and at revs over 3k I was seeing 16V spikes.

Turns out that the plug on the alternator just wasnt seated completely, and the contacts needed to be tweaked a bit to keep contact.

Alll good now.

 

[GEORGE 1992]

Maddening when new parts are bad. Makes you nuts, good thing you diagnosed the high volts, could have caused other problems.

 

[rfiltz]

Just hope I didn't! I drove around a bit with the ECC going on/off! What else should I look for? Once when doing a high rev shift, I noticed the air bag light flashing for awhile. Only did this once or twice and never happened again. I thought my bag would blow while driving down the road!