mrada6998

So I installed a new alternator today, and my battery wont charge. I checked all the fuses, theres continuity from the positive wire back to the battery. So i used a test light on the post on the back of the alternator and nothing. Then I but a test light on the exciter pin, and nothing. So i took the alternator to a couple shops and it tested fine at them all. Why would my exciter wire not be hot?

any ideas?

dreww

iTrader: (1)

What year? Im going thru this issue right now myself.

99 and up the exciter wire goes to the pcm pin 15 and gets about 10v at start up. The pcm is supposed to regulate the voltage to alternator.

If no power to exciter wire, pcm wont tell alternator to turn on or regulate right voltage.

25thhawk

iTrader: (3)

check the exiter wire at the computer, maybe it has a break in it somewhere.
continuity test is easy for that

94 White T/A

If the exciter wire checks good, I wouldn't be surprised if the "new" alternator was bad. Just had a bad one this weekend. most auto parts places sell remans unless you paid $100+ extra for a new one. I've had plenty of new parts not work, just warranty it.

mrada6998

its a 2000 z28. i checked pin 15 and no output. even whent he motor is spinning at 3,000. used a test light right in the pin socket. took the alt out and had it tested and it passed again. If the PCM was bad, the car wouldn't run at all, right?
what would cause the exciter wire to get no power from the PCM?

mrada6998

no ideas?

sreve

iTrader: (3)

Quote: So i used a test light on the post on the back of the alternator and nothing.


That goes back to the battery and should be hot.

badazz81z28

iTrader: (6)

Take the alternator off and have it tested at Autozone? So you can eliminate that variable.

25thhawk

iTrader: (3)

I would use a volt meter. The output is only like 10 volts, it might not light the test light. I would first continuity test the wire from pin 15 to the alternator to make sure there are no breaks.

whitess1

iTrader: (2)

Had a 98 with same problem. There is a 5 volt reference wire had no voltage i found a 5 volt reference wire i believe it was off the egr harness tied into that and it charged fine. Not saying this is the correct way to fix it but it worked for me did not feel like replacing the pcm and messing with the tune