Generator Light
Thread Starter
Heel & Toe
Joined: Sep 2003
Posts: 17
Likes: 0
From: Fort Lupton CO
Generator Light
I bought a '78 Pace Car a few months ago. It has 98,000 miles. It's a little long in the tooth but I absolutely love it!
The generator light stays dimly lit all the time. The voltmeter shows a good charge. The alternator is putting out 14.3V. I've taken the alternator to two places for testing. Both places said the alternator is fine. The service manual says that the alternator field wire is causing the generator light to light. The guy at the second place said he used to work for a Chevy dealer and said this is a common problem with C3s but couldn't remember the fix.
Any ideas?
Thanks, Al
The generator light stays dimly lit all the time. The voltmeter shows a good charge. The alternator is putting out 14.3V. I've taken the alternator to two places for testing. Both places said the alternator is fine. The service manual says that the alternator field wire is causing the generator light to light. The guy at the second place said he used to work for a Chevy dealer and said this is a common problem with C3s but couldn't remember the fix.
Any ideas?
Thanks, Al
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
heres some tech articles..maybe they can help you sort it out...
good luck...
http://www.madelectrical.com/electri...witworks.shtml
http://www.madelectrical.com/electri...hreewire.shtml
this is on voltage sensing
http://www.madelectrical.com/electri...esensing.shtml
good luck...
http://www.madelectrical.com/electri...witworks.shtml
http://www.madelectrical.com/electri...hreewire.shtml
this is on voltage sensing
http://www.madelectrical.com/electri...esensing.shtml
Last edited by bobs77vet; Jan 3, 2005 at 04:24 PM.
Melting Slicks
Joined: Oct 2004
Posts: 2,662
Likes: 8
From: Knoxville Tennessee
I had the same problem with my 79. I took the alternator to a local shop. They checked it out and couldn't find anything wrong with it. I asked them to tear it down and replace the bearings, resistors and diodes as well. For about $50.00 the alternator now works great. I believe that the diodes and resistors inside strat to break down and short with heat.
Bernie
Bernie
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
i had a similar problem with mine (79). alternator light started coming on very dimly at first and intermittently. then more frequently and staying on for longer periods of time, and getting brighter. finally, stayed on all the time. throughout this, my battery always showed about 13.8 volts with engine running and ammeter gauge appeared to show normal charging.
anyway, finally replaced alternator as a precaution (it was at least 15 years old anyway). no more generator light. i think over time, the heat wears out the internals (diodes, etc.).
you can get a cheapo stock replacement alternator (63 amp) at Autozone (can i say that on the Forum) for about $35.00 and see if that corrects the problem.
anyway, finally replaced alternator as a precaution (it was at least 15 years old anyway). no more generator light. i think over time, the heat wears out the internals (diodes, etc.).
you can get a cheapo stock replacement alternator (63 amp) at Autozone (can i say that on the Forum) for about $35.00 and see if that corrects the problem.
Le Mans Master
Joined: Mar 2004
Posts: 7,457
Likes: 1,483
From: Little Rock AR
I would say the diode trio is the problem.
You can replace the diode trio if it is toast. It looks like a small integrated circuit chip with 3 metal leads on one side and a single metal lead on the other. Use your ohm meter to check it. The juice needs to flow through it one way but not the other so check it once then reverse the leads and check again. If one or more of the 3 rectifiers in the trio are bad, the alternator will still work fine but the dash light will glow. Cheap fix.
Mark.
You can replace the diode trio if it is toast. It looks like a small integrated circuit chip with 3 metal leads on one side and a single metal lead on the other. Use your ohm meter to check it. The juice needs to flow through it one way but not the other so check it once then reverse the leads and check again. If one or more of the 3 rectifiers in the trio are bad, the alternator will still work fine but the dash light will glow. Cheap fix.
Mark.
Le Mans Master
Joined: Mar 2002
Posts: 8,575
Likes: 3
From: On an island surrounded by sharks Hawaii
I had the same problem on my 79 and after confirming that the alternator and battery were all good it turned out to be corrosion on the fuse and fuse panel. Check the fuse and fuse panel that say 'gauge', cleaned them up and problem cleared.HTH
Burning Brakes
Joined: Feb 2004
Posts: 958
Likes: 1
From: In the Beautiful Shenandoah Valley of VA
Originally Posted by stingr69
I would say the diode trio is the problem.
You can replace the diode trio if it is toast. It looks like a small integrated circuit chip with 3 metal leads on one side and a single metal lead on the other. Use your ohm meter to check it. The juice needs to flow through it one way but not the other so check it once then reverse the leads and check again. If one or more of the 3 rectifiers in the trio are bad, the alternator will still work fine but the dash light will glow. Cheap fix.
Mark.
You can replace the diode trio if it is toast. It looks like a small integrated circuit chip with 3 metal leads on one side and a single metal lead on the other. Use your ohm meter to check it. The juice needs to flow through it one way but not the other so check it once then reverse the leads and check again. If one or more of the 3 rectifiers in the trio are bad, the alternator will still work fine but the dash light will glow. Cheap fix.
Mark.
Steve
