GEN Light on
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 47
Likes: 1
GEN Light on
Hello
Just bring back my 1977 vette from the mechanic for breack check and now the GEN light ramain on after the engine is started.
I don't think is related to the job made on the break.
Any suggestion ?
Thanks
Just bring back my 1977 vette from the mechanic for breack check and now the GEN light ramain on after the engine is started.
I don't think is related to the job made on the break.
Any suggestion ?
Thanks
Burning Brakes
Joined: Sep 2006
Posts: 1,071
Likes: 86
From: Rotonda FL
1) What does your voltmeter read? If it is straight up, pointing at 13, and remains so as the engine continues to run, your alternator is supplying current to the system.
2) Look at your alternator. There should be an 18/20 gauge brown (or possibly white) wire attached to it. This wire goes back to the plug in back of your center gauge cluster, and then to the GEN light. It performs 2 functions - a) it excites the alternator when starting, and b) Warns you when the oltage at the alternator is less than the voltage in the battery. If it is disconnected, your GEN light will come on.
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
Several things to look at:
1) What does your voltmeter read? If it is straight up, pointing at 13, and remains so as the engine continues to run, your alternator is supplying current to the system.
2) Look at your alternator. There should be an 18/20 gauge brown (or possibly white) wire attached to it. This wire goes back to the plug in back of your center gauge cluster, and then to the GEN light. It performs 2 functions - a) it excites the alternator when starting, and b) Warns you when the oltage at the alternator is less than the voltage in the battery. If it is disconnected, your GEN light will come on.
1) What does your voltmeter read? If it is straight up, pointing at 13, and remains so as the engine continues to run, your alternator is supplying current to the system.
2) Look at your alternator. There should be an 18/20 gauge brown (or possibly white) wire attached to it. This wire goes back to the plug in back of your center gauge cluster, and then to the GEN light. It performs 2 functions - a) it excites the alternator when starting, and b) Warns you when the oltage at the alternator is less than the voltage in the battery. If it is disconnected, your GEN light will come on.
This^^^^^^^
I doubt that the alternator just failed at the mechanic BUT it could. More likely the mechanic touched a wire ^^^^^^ causing the Gen light to illuminate
Safety Car
Joined: Sep 2012
Posts: 4,688
Likes: 41
From: Palm Harbor, Florida
This problem can be a real hassle. I've had it many times in the past, chasing different things. I eventually sent it in to a mechanic(which takes a lot for me), he put on a self exciting alternator, never had the problem again.
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 47
Likes: 1
Do you have a link to the self exciting alternator?
What does it mean self exciting?
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
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Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
He didnt fix it, he bypassed it.
Le Mans Master
Joined: Jan 2001
Posts: 6,741
Likes: 1,383
I suspect that it is associated with the job on the brakes; not definitely, from my experience of messing with things. If your alternator is putting out 13 VDC then the is charging (assuming your battery terminal voltage when off is about 12 VDC). but it really should be maintaining closer to 14 VDC
What was he doing to the brakes? Perhaps we can narrow down the search area.
What was he doing to the brakes? Perhaps we can narrow down the search area.
Last edited by carriljc; Dec 9, 2018 at 08:24 AM. Reason: Added bold text --
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 47
Likes: 1
I suspect that it is associated with the job on the brakes; not definitely, from my experience of messing with things. If your alternator is putting out 13 VDC then it is charging (assuming your battery terminal voltage when off is about 12 VDC).
What was he doing to the brakes? Perhaps we can narrow down the search area.
What was he doing to the brakes? Perhaps we can narrow down the search area.
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
No less than 13.8 volts generally under load.
A fully charged battery under no load could be as low as 13.2-13.4...........
Much depends on the alternator type, revs, load, etc........
There really is no set number...except it should be more than 13 volts generally....
Last edited by jb78L-82; Dec 4, 2018 at 02:36 PM.
Safety Car
Joined: Sep 2012
Posts: 4,688
Likes: 41
From: Palm Harbor, Florida
here's a link. Much better price than the one I just got for my 02 vette, it was $380 on amazon. C5 needs to have the internal circuitry to communicate with the PCM.
Last edited by Doug1; Dec 5, 2018 at 06:13 PM.
Safety Car
Joined: Sep 2012
Posts: 4,688
Likes: 41
From: Palm Harbor, Florida
Safety Car
Joined: Sep 2012
Posts: 4,688
Likes: 41
From: Palm Harbor, Florida
I suspect that it is associated with the job on the brakes; not definitely, from my experience of messing with things. If your alternator is putting out 13 VDC then it is charging (assuming your battery terminal voltage when off is about 12 VDC).
What was he doing to the brakes? Perhaps we can narrow down the search area.
What was he doing to the brakes? Perhaps we can narrow down the search area.
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 47
Likes: 1
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
Please check the voltage with the engine running at an idle. The standard is 1 volt over battery voltage. A fully charged battery is 12.6 volts, so your minimum voltage should be 13.6 volts.
Voltage is just part of the electrical output, the other measurement is amperage. The alternator could be putting out voltage but not sufficient amperage. If you do as previously suggested and have the unit tested at Autozone they will tell you if it's performing properly. After checking all of the wire connections, and broken wires, testing the alternator would be next on the list
Voltage is just part of the electrical output, the other measurement is amperage. The alternator could be putting out voltage but not sufficient amperage. If you do as previously suggested and have the unit tested at Autozone they will tell you if it's performing properly. After checking all of the wire connections, and broken wires, testing the alternator would be next on the list