78 vette GEN light glowing

[White75]

I took the 78 vette out this weekend and the GEN light was on. At higher RPMs it would dim down but never really turn off. The voltmeter showed 13 and she seemed to run normal. The battery is about a year old.
I'm pretty sure the alternator is original but not 100% sure (Don't see any record of it being replaced). What should I look for to see if I have a bad alternator, voltage regulator, or anything else this could be. Now that the triple digit temperatures have taken a hiatus, I want to drive but don't want to get stuck by something that has already shown signs of failing. I really hate diagnosing electrical issues so any assistance would be great.
Thanks!

 

[LLC5]

I took the 78 vette out this weekend and the GEN light was on. At higher RPMs it would dim down but never really turn off. The voltmeter showed 13 and she seemed to run normal. The battery is about a year old.
I'm pretty sure the alternator is original but not 100% sure (Don't see any record of it being replaced). What should I look for to see if I have a bad alternator, voltage regulator, or anything else this could be. Now that the triple digit temperatures have taken a hiatus, I want to drive but don't want to get stuck by something that has already shown signs of failing. I really hate diagnosing electrical issues so any assistance would be great.
Thanks!

It sounds like a bad diode trio in the alternator. There are testers for just that (I actually have one which is showing my age). It can affect the output of the alternator so it would be a good idea to take care of the issue. Good luck with it.

 

[White75]

Where would that be located at and how do I test it (take it to AZ?)

 

[gmjunkie]

I took the 78 vette out this weekend and the GEN light was on. At higher RPMs it would dim down but never really turn off. The voltmeter showed 13 and she seemed to run normal. The battery is about a year old.
I'm pretty sure the alternator is original but not 100% sure (Don't see any record of it being replaced). What should I look for to see if I have a bad alternator, voltage regulator, or anything else this could be. Now that the triple digit temperatures have taken a hiatus, I want to drive but don't want to get stuck by something that has already shown signs of failing. I really hate diagnosing electrical issues so any assistance would be great.
Thanks!

Alternator is probly on it's way out!~!!
With the dimming of the light at higher RPM,My guess is the brushes are worn out!
You can purchase a rebuild kit from Blue Chip that come complete with Bearings,Brushes,New Brush holder W/springs,Diode Trio and Voltage Regulator W/Complete Instructions for about $17.00 and re-build it your self in about an hour if you have a few basic tools and a VOM!~!!

 

[Vettehead Mikey]

With only 13V at high RPM, the battery is not being charged. Should have at least 14.2 to 14.5. Like Junkie said, rebuild the alternator.

 

[White75]

thanks guys. If I ever get some time, I'd love to rebuild it, especially if it is the original one. In the meantime, do you see any issue with swapping my 75's L48 alternator to the 78's L82 to make sure it's the alternator and to allow me to drive it if I want (alternator swapping looks pretty quick so I can swap back if I feel like driving the 75.

 

[Vettehead Mikey]

That should work just fine.

 

[White75]

Hey junkie,
do you have a link to blue chip? all my searches find stock trading companies

Alternator is probly on it's way out!~!!
With the dimming of the light at higher RPM,My guess is the brushes are worn out!
You can purchase a rebuild kit from Blue Chip that come complete with Bearings,Brushes,New Brush holder W/springs,Diode Trio and Voltage Regulator W/Complete Instructions for about $17.00 and re-build it your self in about an hour if you have a few basic tools and a VOM!~!!