1977 "GEN"-Light flashes - Generator is okay - what to check?

[Oliver B.]

In my 1977 the red GEN-Light in the center console flashes intermittently. The output of the Generator checks a-okay, so I assume some wiring/ground-problem... This may be supported by the fact that the flashing stops when I switch on the AC. (?)

Any hint, what/where to look for?

Thanks for your help
Oliver

[Joe R.]

Re: 1977 "GEN"-Light flashes - Generator is okay - what to check?

Oliver,

The flashing stops when the AC is switched on because the idle solenoid increases the idle to compensate for the drag put on the motor by the AC compressor. The flashing is caused by a slow idle RPM. If you want to get rid of the nagging flashing generator light just increase the idle speed by a hundred or so rpms when the AC is not on.

JR

[Oliver B.]

Re: 1977 "GEN"-Light flashes - Generator is okay - what to check?

Thanks, Joe. Sounds reasonable - BUT I am getting the flashing light while driving, not in idle...

[Joe R.]

Re: 1977 "GEN"-Light flashes - Generator is okay - what to check?

Thanks, Joe. Sounds reasonable - BUT I am getting the flashing light while driving, not in idle...

Oliver,

I'm out!!!! Good luck!!!!

JR

[Oliver B.]

Re: 1977 "GEN"-Light flashes - Generator is okay - what to check?

Many thanks, anyway, Joe!

[Alan D.]

Re: 1977 "GEN"-Light flashes - Generator is okay - what to check?

Oliver,
Check and make sure there is a good ground at the alternator. Is the voltage meter working correctly? If it has a bouncing indicator needle, it is a poor ground.
Has the alternator been rebuilt? If not it could be the alternator. Does the voltage meter drop when th gen light comes on?
Al Dieterle

[Edward J.]

Re: 1977 "GEN"-Light flashes - Generator is okay - what to check?

Oliver, The alternator can still have some or most of its output. Its likely you have a diode trio gone or the rectifier bridge gone. If you checking the voltage output it should be about 13.8/14.2 volts@ idle. With the voltage regulator grounded the amperage output should be about 75 percent of its output.

[Russell O.]

Re: 1977 "GEN"-Light flashes - Generator is okay - what to check?

Oliver, as I am an owner of 1977 corvette, I have seen this very issue many years ago. Now since I have owned that car for 23 years, I am trying to remember how exactly I fixed mine. I know I didn't change my alternator, so but to my knowledge, I think I just adjusted my idle up a bit. Now I say that because you stated that when you turn your AC on, it turns off, and when you turn your AC on, your idle kicks up a bit. So I think you should recheck your timing and adjust your idle an see what happens. Does the light turn off when you get above a certain RPM? If you don't find the answer that solves your problem, LMK and I will talk to corvette guy here in OKC that knows these cars inside and out.

Also, have the battery checked.

Russell

[Oliver B.]

Re: 1977 "GEN"-Light flashes - Generator is okay - what to check?

Thanks for everybody's feedback...

Here answers to some of your hints:

@ Alan - the voltmeter's needle doesn't bounce at all and the voltage doesn't go down when switching on the lights. (But I'll make sure about that once again.) I had the alternator's "regulator" changed some 15 years ago, and that's about all I did to it.

@ Edward - diode trio/rectifier bridge; it can well be that this is what was changed back then (the "regulator"?) - but then the GEN light was bright red all the time and only dimmed when rpm increased a lot... Furthermore the voltage reads @ what you say it should...

@ Russell - actually my rpm do drop when putting the AC-load on top. And as the flickering occurs at ordinary cruising speed, I would say it's nothing with idle rpm.

Anything else? ...But I will check out voltage and a possible drop when switching on the lights again...

Thx