Erratic Ammeter Behavior – Seeking Advice

RM21H9-SunfireYellow

RM21H9-SunfireYellow

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Last night, after driving for about an hour, my ammeter gauge started acting erratically. For context:

  • I drove during daylight for an hour with no issues.
  • Parked for about an hour.
  • When I left, it was dark, so I turned on the headlights and drove off.

About 20–30 minutes into the nighttime drive, the ammeter began jumping back and forth—then settled briefly—then started again. While this was happening, the instrument cluster lights flickered in sync with the gauge: dimming during discharge and brightening during charge.

I made it home and checked the wiring around the alternator and bulkhead. Everything looked okay, but clearly something’s off.

Any ideas on what could be causing this? I’d really appreciate any guidance or suggestions.
 
Bad Ground ? you can't have enough I run 3 core support , firewall , engine. Also I am running a 130 ALT (tuff stuff ) and a matching REG

Tuff Stuff Performance 7524 Alternator Replacement Voltage Regulator amazon​

 
the amp meter in the dash is getting hot look under the dash and you will see if the wires are loose or is the insulator broken and shorting out . REMOVE THE NEGATIVE BATTERY CABLE so not to burn down the car

i hope im wrong and it is the regulator as said above and yes check the ground from the engine to battery and the engine to body ground cable are clean and no paint or rusted clean.
 
Well, I found out the hard way. Short answer: The alternator failed. I checked all the wiring connections at the alternator, but nothing appeared suspicious. I also checked the wires on the ammeter; they were good, and the ammeter didn't feel warm or hot to the touch. So I went for a test drive, everything was running good. Then the ammeter started acting erratically, the engine started to die, there was a loud backfire, and then the car went dark. Lucky for me, the fuseable link worked. The link burned, and the bulkhead connector melted a bit. After this happened, I checked the wiring again, and I found the charge post on the alternator was loose. The wire is tight to the post, but the whole post is loose. This wiring is original, which means it is time to replace all of it from bumper to bumper. I know there are factory replacement kits out there. Now I need to find the right one for this car.

Thank you all for your ideas & suggestions.

RR Flatbed.jpg
 
V.R.D said:
the amp meter in the dash is getting hot look under the dash and you will see if the wires are loose or is the insulator broken and shorting out . REMOVE THE NEGATIVE BATTERY CABLE so not to burn down the car

i hope im wrong and it is the regulator as said above and yes check the ground from the engine to battery and the engine to body ground cable are clean and no paint or rusted clean.
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In
RM21H9-SunfireYellow said:
Well, I found out the hard way. Short answer: The alternator failed. I checked all the wiring connections at the alternator, but nothing appeared suspicious. I also checked the wires on the ammeter; they were good, and the ammeter didn't feel warm or hot to the touch. So I went for a test drive, everything was running good. Then the ammeter started acting erratically, the engine started to die, there was a loud backfire, and then the car went dark. Lucky for me, the fuseable link worked. The link burned, and the bulkhead connector melted a bit. After this happened, I checked the wiring again, and I found the charge post on the alternator was loose. The wire is tight to the post, but the whole post is loose. This wiring is original, which means it is time to replace all of it from bumper to bumper. I know there are factory replacement kits out there. Now I need to find the right one for this car.

Thank you all for your ideas & suggestions.

View attachment 39336
Click to expand...
 
Sorry for your luck. When restoring my 69. Replaced all the wiring with new. Just had the problem with amp meter wire. Lost all power to car. I would get power then lose it. Had to tighten the first nut on stud coming out the back of gage
. Then place the eyelet from wire on them tighten it. Have 6000 miles on car since restoring it. It has had to take a ride on the tow truck a few times. Once a new start run relay went bad. So don't remember what the other things where. We do our best but some times things just happen. I have ordered a troll doll to hang on the mirror to word off the jinks. We had them in the sixties in our cars. Lol. Do they work but dout it. But it made us feel better. So now you are learning about classic cars and what they are about. At least we don't have to get a computer geek to work on them. Lol.
 
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