Alternator gauge is smoking

[67Dart273]

All Amp meters have a shunt (a bypass resistor) across the meter to carry the high current around the meter movement. It sounds like the meter shunt is damaged. The shunt may be internal to the meter. Can you try using the old meter to see if the problem clears up?

Mopar ammeters have no such thing. --That is, the ones we are discussing, the "full current" ammeters and not the "external shunt" type.--- If you ever disassemble one, you'll see. The entire "meter" consists of the brass piece which "is the shunt" and the needle assembly which sits adjacent to it with a vane device. What CAN happen is the studs can become loose as I've previously described.

 

[Captain Easy]

Load is one thing, resistance is another. Smoke requires heat, heat is a function of resistance. I've had a few situations of corrosion with that era of Mopar ammeters. It can be invisible to the eye. I've had essentially invisible corrosion on the ammeter terminals and circuit board bad enough to actually shut the car down as no current could pass (which I suppose is better than having enough current to run but enough resistance and heat to start a fire). Even if they look good, clean those terminals well, an d make sure the electrical transition from the threaded lugs to the shunt is solid. You can test with a charged battery and an old fashion heat resistance battery load tester, on the bench, and see what smokes...

 

[Mattax]

All Amp meters have a shunt (a bypass resistor) across the meter to carry the high current around the meter movement. It sounds like the meter shunt is damaged. The shunt may be internal to the meter. Can you try using the old meter to see if the problem clears up?

I used to think similarly but as already explained that is not so in these cars.
It can be true, especially in test equipment. Like illustrated here in where Chrysle rcplains how the test instruments work and how to use them.

In the car's dashboard ammeter we can call the metal carrying the current a shunt but its not technically correct so I don't anymore. It's plate creating a magnetic field that moves the needle. There is no permanent magnet and there is no coil. It would not surprise me a bit if this is the same way an ammeter works on a Jeep MB or CJ, and many other vehicles of that era.
On a remote shunted ammeter, the resistance is in the meter and the shunt is the low resistance path that carries most of the current in parallel.
1976 A-bodies got a remote shunted ammeter in the dash.

 

[67Dart273]

Yup, thing is there are kinds of "meters." The Mopar type is just a vane that reacts with magnetism in the brass strip. Closest thing you can call it a shunt, but it doesn't actually shunt anything. You can (used to could) buy "quick test meters" that you simply hold around a wire work similar, and way back in the day (58--63-ish?) one of the school busses had a dash ammeter that worked that way. Here are some various types

These are sometimes called "clip on" or "induction" which is not quite technically correct

This Sears one is being shown "either or" The "smaller" wire side is for charging system, the larger is for starter current

 

[512Stroker]

Hey all, I just installed a new gauge cluster in my 1972 duster and when the car is running smoke comes from the alternator gauge pegs. I’m not sure why this would be, I’m wondering if anyone had a similar issue or knows the fix? Thanks

Some Mopars owners choose to bypass the ammeter altogether and/or replace it with a volt meter. Apparently there have been a number of cars burnt because of such issues.
Good luck

 

[Col_Steve]

I always solder the stud heads to the brass lugs (green ovals on your picture) prior to installing any ammeter new or used. Use a hot 100 watt iron on the flat stud head, add a dab of solder to the intersection of the iron and stud head to initiate heat transfer, when that dab melts to where it wets the head of the stud add more solder to the rim of the stud head and it will flow around and under the head of the stud permanently bonding it to the brass lug of the ammeter. Ammeters with loose studs or deformed lugs can be saved in the same manner but all surfaces must be abraded to a shiny metal finish and the lugs must be straightened out prior to soldering. Doing this eliminates the perceived need to overtighten the ammeter attachment nuts. The wire eyelet nuts should be rather tight and the nuts need to be the ones with the radial lock grooves stamped into them. Prior to installation make sure the ammeter nuts and wire eyelets are shiny clean. Previously overheated ones will be dark gray or blued with oxidation and must be cleaned or replaced. If you replace a wire eyelet it must be crimped AND soldered to the wire, not just crimped. Crimped only will fail...every time. It is good practice to install a 12 gauge bypass wire directly from the alternator output stud to the starter relay stud. This will halve the current seen by the ammeter. Yes, I know the ammeter will not move as much as it did prior to the bypass, but it will still indicate charge/discharge, and it will not get hot anymore. You will have better headlights as a bonus.

 

[4spdragtop]

I'm sure this has been mentioned, but have u checked the bulkhead connectors for the alt gauge?

 

[Mattax]

And as usual we have taken the thread into theoretical side track. LOL.

Really should wait for @67cudaGuy post back with more info or questions.
All we know is
there was smoke under the dash when the engine was running.
the ammeter was pegging ? but dont know which way.
does not look like the ammeter saw heat.

 

[Dartswinger70]

My dad had a 66 Coronet that had a dash fire around 1971 or 72...I bet something like this may have been the culprit. People always said he left a cigarette in the ash tray he always said that wasn't it...