Voltage to Exciter Wire When Off?
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From: SD
Voltage to Exciter Wire When Off? 2000 LS1 here. My alternator makes a high pitched electrical noise when the car is off. I tried a second alternator, but the noise persisted. So i pulled the alternator plug and found that the exciter wire (red pcm pin15) is putting out 5v when the key is off. Does anybody know what voltage should be when off? I was thinking it should be zero??
yes it should be zero. when the pcm puts 5v on that "exciter wire" to the voltage regulator that is the turn on signal telling the alternator to charge.
if the pcm doesn't put 5v on that wire or the voltage regulator doesn't receive 5v on that terminal then the alternator will not output.
if the voltage regulator connects that exciter wire terminal to ground (electronically within the voltage regulator) that is how the pcm knows the alternator is bad.
so what have you done to your car?
if the pcm doesn't put 5v on that wire or the voltage regulator doesn't receive 5v on that terminal then the alternator will not output.
if the voltage regulator connects that exciter wire terminal to ground (electronically within the voltage regulator) that is how the pcm knows the alternator is bad.
so what have you done to your car?
Thread Starter
Teching In
Joined: Oct 2009
Posts: 8
Likes: 0
From: SD
Thanks for the response, looks like I have some troubleshooting to do. The engine/transmission are a transplant and the harness has been modified. I'm guessing that something got messed up when I reworked the harness.
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Joined: Aug 2018
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yes it should be zero. when the pcm puts 5v on that "exciter wire" to the voltage regulator that is the turn on signal telling the alternator to charge.
if the pcm doesn't put 5v on that wire or the voltage regulator doesn't receive 5v on that terminal then the alternator will not output.
if the voltage regulator connects that exciter wire terminal to ground (electronically within the voltage regulator) that is how the pcm knows the alternator is bad.
so what have you done to your car?
if the pcm doesn't put 5v on that wire or the voltage regulator doesn't receive 5v on that terminal then the alternator will not output.
if the voltage regulator connects that exciter wire terminal to ground (electronically within the voltage regulator) that is how the pcm knows the alternator is bad.
so what have you done to your car?
Last edited by Shotz89; Aug 21, 2018 at 01:17 AM. Reason: Spelling
