Driving down the road, sometimes the needle pegs. Headlights are brighter too. Then 500' later, there's an audible click and the needle goes back to normal.

Would this be an alternator or regulator issue. Both are what was on the truck (74 w200) when I bought it. I don't want to just throw parts at it, since money is super tight right now.

(1) either there's an part time open in the field circuit that depletes the system for awhile (do you see a discharge/lights dim) then when it restores contact the system full fields to restore the charge & that is the click you hear as the alt is now back engaged or (2) something is full fielding the green wire field circuit part time which is kinda rare. not the reg cuz electronic ones either go open or full field and stay that way. for #2 do a visual on the brushes on the alt (anything loose/close to touching) and check the terminals on the green wire at the reg and alt ends for where it might be intermittently grounding to metal which is what is full fielding it (& the green wire along its length for any exposed copper strands that might be grounding to something metal close by from vibration as the truck is being driven), otherwise for #1 clean the bulkhead then the rest of the terminals/connections in the blue wire ign1 (run) field circuit as needed but start with the bulkhead

Wire harness is off a known running driving truck. I had to re pin it (re arrange wires) and at that time, I cleaned the terminals.

Both ends of the green wire are in ok condition. The truck it came off of had no issues with charging or discharging except at idle with all accessories on.

I do not know if the truck did this before I swapped wiring harnesses. I started tracing wires and the "custom" wiring harness on this truck was flat 4 pin trailer wiring. I was tracing wires because they had the coil wire ran directly from the ballast and bypassed the wiring loom and I wanted to find out why.

Alternator and regulator sat unused for 12 years. Could putting it back into use damage it? Other thing I can think of, is that the lady hosed off the engine bay and probably soaked the alternator.

OK we know the wiring is (now) routed correctly. I'd never suggest shotgunning new part purchases for diagnosing but I'd be nice if you had another alt in your stash that you could sub in for a quick test in that regard. Right now I think I would clean the reg ground and unplug and plug back in the reg connector and the field terminal connectors and inspect the brushes & maybe take the alt in & have em spin it & see if it acts up during the testing there. This does need to be addressed ASAP as even brief full fielding will fry bulbs/electrical devices cuz they ain't meant to recieve 15-16V (or shorten their lifespan)

I am going to guess that something on the ign ( run) side is pulling the voltage down (click) and thereby telling the alternator to CHARGE. The regulator uses the RUN side of the ign circuit to sense the available voltage and control the alternators output.
The symptom sounds like a circuit breaker resetting itself, sensing the overload and tripping again.

I would try to identify where the CLICK is coming from. I might suggest to look at anything that has been added to the truck especially if it's using a relay.

Ok, so went back through the wiring.

Didn't find anything out of the ordinary, but decided to put on another known good VR.

Doesn't have an overcharge now, but needle is jumping around. Turn headlights on, and it jumps up towards charge and then right back down. It also goes up and down with the blinkers.

Not sure if this is normal. Other trucks I've had, the needle was real steady. I have an extra 78 amp alternator I can put on there, if the needle being erratic is not normal.

Not normal, swap that puppy in there

Just a FYI I swapped alt and regulator to solve the problem with my wiring burning from Alt back. It's been good now 250 miles and 3 weeks listen to Rapid and swap it his advise is good !

I had a similar problem with my Dart years ago. Turns out, one of the bolts that held my regulator to the firewall was stripped. The connections got bad, rusty and then the regulator wouldn't ground properly. This would cause it to go full charge and blew out my high beams twice before I figured out what the issue was.

So, make sure your regulator is bolted down tight and the surfaces are clean. Adding a secondary ground wire is also not a bad idea. You can never have enough grounds.



That's normal operation for an ammeter that does not use a Shunt - like pre-'78 Mopar ammeters. All you're seeing is what your alternator is doing.

Ammeters with a shunt are much slower to react and often times don't look like they ever move.

I had the same problem with a 74 Charger that had a new paint job. Super bright headlights and a little wisp of smoke from under the dash. For me it turned out to be the firewall ground for the voltage regulator. I sanded the paint on the firewall and regulator. I also added a ground wire to each module on the firewall. No problems since then.