Weird problem
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Joined: May 2012
Posts: 69
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From: Cumming GA
Weird problem
Little background - 94 coupe with 6 speed manual - about 135K on the clock.
Recently replaced; the optispark, water pump, alternator (ac Delco) and battery (interstate). All was running well. Took it to work this morning, no problem.
On the way home tonight, the dash lights dim, the voltage gauge goes from like 14 to 10 and the battery light comes on in the DIC. Stays like that for a few seconds and then goes back to normal brightness, 14 volts and the battery light goes off.
Seems to be ok under throttle, but gets flaky when coasting.
checked all the battery/alternator connections and they are tight. Pulled the codes when I got home and got C72 and H73. Don't think either is at the root, as I have had before and don't believe they are directly related.
Any ideas on where to start troubleshooting?
Appreciate your insights.
Recently replaced; the optispark, water pump, alternator (ac Delco) and battery (interstate). All was running well. Took it to work this morning, no problem.
On the way home tonight, the dash lights dim, the voltage gauge goes from like 14 to 10 and the battery light comes on in the DIC. Stays like that for a few seconds and then goes back to normal brightness, 14 volts and the battery light goes off.
Seems to be ok under throttle, but gets flaky when coasting.
checked all the battery/alternator connections and they are tight. Pulled the codes when I got home and got C72 and H73. Don't think either is at the root, as I have had before and don't believe they are directly related.
Any ideas on where to start troubleshooting?
Appreciate your insights.
Le Mans Master
Joined: Sep 2009
Posts: 6,338
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From: Vermilion OH
I would hook the positive lead of a multi-meter to the positive output on the alternator and ground the other lead and see what your voltage output is directly from the alternator at idle. Sounds like the alternator may be failing.
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Joined: May 2012
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From: Cumming GA
Melting Slicks
Joined: Apr 2011
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From: New Jersey
This could be the alternator but not necessarily so. I do not know if a 94 still has the terminal block for all of the hot feeds behind the battery, but if it does please check it. I had these exact symptoms and assumed alternator. Not only did I buy an alternator I didn't need, but I also discovered that the wires at the terminal block were arcing/melting. There could have been a serious fire if left unaddressed.
Thread Starter
Advanced
Joined: May 2012
Posts: 69
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From: Cumming GA
This could be the alternator but not necessarily so. I do not know if a 94 still has the terminal block for all of the hot feeds behind the battery, but if it does please check it. I had these exact symptoms and assumed alternator. Not only did I buy an alternator I didn't need, but I also discovered that the wires at the terminal block were arcing/melting. There could have been a serious fire if left unaddressed.
M
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Joined: May 2012
Posts: 69
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From: Cumming GA
UPDATE - So I check ed the battery and alternator with a multi-meter. Battery was about 12.7v at outset. Started car and went to 14.6, still what I would call normal. Put electrical system under load - headlights/fog lights/radio/ HVAC fan and it dipped to 14.1, but still good.
Turned the car off and the battery was 13.1, so I am getting a charge.
Looked for any arcing and did not see any.
Did notice that the voltage variability only seems to kick in north of 1,500 rpms. Anything less and it is rock steady. Over 1,500, will drop to 12.7 - 13.0v and peg there for a few seconds and then go back up to 14.7. Did see it shoot up to 15.1 too.
Don't feel any unusual vibration, so not noticeably shaking anything loose.
Flaky alternator?
Turned the car off and the battery was 13.1, so I am getting a charge.
Looked for any arcing and did not see any.
Did notice that the voltage variability only seems to kick in north of 1,500 rpms. Anything less and it is rock steady. Over 1,500, will drop to 12.7 - 13.0v and peg there for a few seconds and then go back up to 14.7. Did see it shoot up to 15.1 too.
Don't feel any unusual vibration, so not noticeably shaking anything loose.
Flaky alternator?
