ammeter

[Diane76]

Hi,

I have a '76 Corvette. I would appreciate if someone can please give me some help concerning an ammeter problem and smoke condition. The ammeter needle got stuck on the negative reading edge. It had smoke behind the gauge glass and smoke in the cabin. I would like to know, what is in the circuit with the ammeter - is it just the alternator? What is the correct procedure to take for diagnostic? What is the most time you can envision a diagnostic would take? Can the circuit be checked with a multimeter or the car should not be turned on? Is there anything indicated by that a fuse did not blow? Should a test be run across the fuse terminals? All the other instruments were working fine before turning the car off because of smoke. Does this mean the main wiring harness is okay? I was told the harness burns up pretty quick and there was significant smoke.
Would it be safe to just test the ammeter itself and if there's no current, replace it and take the car for a test drive? I was told there's a generally known problem with ammeters from '63's upward. Have you heard of this?
Thanks very much for your time.

[Diane76]

Is there someone on here who can help me with these questions pls? Tech staff?

[LLC5]

Originally Posted by Diane76

Is there someone on here who can help me with these questions pls? Tech staff?

I am not sure about a '76 ammeter. I need to know if it is a full current ammeter, or a inductive style ammeter. I will do some research. If you know the answer for sure (no guessing, that will be counter productive), let me know. Also, this is a stock OEM meter correct, and not and aftermarket meter, correct?

[Diane76]

Hi,

Yes it is a stock ammeter. I'm sorry that I don't know what type of current. I appreciate your time. Thank you.

[LLC5]

Originally Posted by Diane76

Hi,

Yes it is a stock ammeter. I'm sorry that I don't know what type of current. I appreciate your time. Thank you.

From what I have found, it looks like an inductive ammeter from the pictures that I have seen, which would mean that possibly not too much damage has probably occured. If it is a full current ammeter, then there is a possibility that the harness is burned. Either way, you need to remove the ammeter and assess the damage behind it, since you stated that smoke came out of it. The smoke could be from the ammeter, or the harness behind it, or both. I would recommend dissasembling the gauge assembly that houses the ammeter and see what happened. You don't want to drive a vehicle in that condition. No circuit check will tell you the needed repairs behind the meter, you need to do a visual to see the extent of damage. Good luck with it.

[Diane76]

Thanks very much for your reply.
I'd appreciate if you can please tell me:
why does an inductive ammeter indicate there is probably not much damage?
does the whole dash need to be removed, or just part?
would you expect that if anything else burned, it would be right behind the ammeter, not farther along the circuit?
how long do you think a visual check could take at maximum?

thanks so much

[LLC5]

Originally Posted by Diane76

Thanks very much for your reply.
I'd appreciate if you can please tell me:
why does an inductive ammeter indicate there is probably not much damage?
does the whole dash need to be removed, or just part?
would you expect that if anything else burned, it would be right behind the ammeter, not farther along the circuit?
how long do you think a visual check could take at maximum?

thanks so much

With an inductive ammeter it senses voltage drop and doesn't carry full vehicle current. A full current ammeter does carry full vehicle current, and if there is a heavy short to ground that is unfused, it will burn the wires from the source to the short which in your case sounds like it may have gone through the ammeter also. An inductive ammeter is in parallel, and the full current ammeter is in series. Since the inductive style ammeter doesn't carry full vehicle current, then the smoke you have seen may have just been the gauge going bad, but you need to disassemble to verify. I think just your center stack where the ammeter is housed will need to come out, after that you can determine how extensive the damage is, then you will know how much else has to come apart, if at all. I would think you might be looking at 2-4 hrs to disassemble and diag, but that is just a guess as it has been a very long time since I have seen that year vehicle.

[Diane76]

Thank you very much for all of your help!

[LLC5]

Originally Posted by Diane76

Thank you very much for all of your help!

No problem. I hope it helps in some way.

Good luck with the repairs.