hi , I have a 1970 road runner .it charges acoording to amp guage when I accelerate. when I idle it starts to discharge rather than charge. if I have directional or lights on if idling it really discharges bad and runs rough. I replaced alternator and regulator. ive had vehicle for 30 plus years and this just started happening. I also changed battery.any tips would be appreciated.thanks

Search around on here. plenty of info on this topic. Start with cleaning the bulkhead connector.

I had the same exact thing happen and it was that I needed to rewire the charging system as well as find out that my supposedly good alternator was not so good. It took three different alternators to find a good one. It's just that bad in today's world of crappy parts. I upgraded from a 40 AMP to a 60 AMP out of a C-body and got rid of the stock AMP gauge for an under dash Voltmeter.

Now all is fine and works like its supposed too.

Few more photos:

im going to take alternator out of my cuda and see if I have same problem. I recently had guage cluster out and wonder if its related. it charges fine when you give it gas but at idle, in drive it goes under 12 volts.thnx

Clean all the grounds amd make sure they are all in place.

I'm thinking the reg even tho you changed it out. (Mechanical or electronic reg?). Might full field the alt for 3 seconds & see if it's (the alt) is OK. (have lights/acc OFF). IF the alt & reg are OK & the batt is charged then that only leaves the supporting Wiring: alt/reg field wiring on the positive side, grounds on the neg side, poor connection that just developed cuz it was OK for years & as said the bulkhead is a frequent offender. Holler how it goes.

im going to take alternator from my cuda and see if its better. I changed reg and battery from working cuda but it didn't help.thank you

"food for thought". A high output alternator(65amps and up), won't put out at low RPM. A standard alternator (35amp) will put out at a lower RPM. Maybe what you are experiencing is normal for the alternator you are running. Check what amp your alternator is before panicking.

its supposed to be a 60 amp.if im waiting at traffic light with brake pedal on ,directional and cd player on it starts to discharge really bad and starts running really rough probably cause its discharging bad.when I start driving it charges really good till it evens out.thanks

ive had everything the same for years.does ballast resistor have anything to do with it. ill change alt from my cuda next weekend.thnx

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its supposed to be a 60 amp.if im waiting at traffic light with brake pedal on ,directional and cd player on it starts to discharge really bad and starts running really rough probably cause its discharging bad.when I start driving it charges really good till it evens out.thanks

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I'll probably get some "push back" from others on this suggestion, but it's worked for me for many, many years.
Try a "constant output" regulator. It puts out 13.5 volts all the time. Some say that it will over charge the battery, but I've NEVER had an issue with mine.

if it wasn't fathers day I would take my cuda alt out today and put it in road runner. I swore I would not work on cars today. I drove cuda today and charges great. ill post back hopefully next weekend when I switch out alt.,thnx

I'm reading your posts as no new electrical stuff has been added to create more draw. I'm going to say a good cleaning will get you back in business like you were.

hope so. ill try next weekend.thnx

Been driving my challenger since 2005 with a #10 wire from the alt to the starter relay, so my amp gauge don't work. Car seemed to run fine and always started.

Then a couple weeks ago I put my headlites and AC clutch on relays. Noticed the lights were still dimming at idle with the AC cranked on high.

So I picked up this cheap DVM that plugs in my cig lighter. I had less than 12 volts at idle and maybe 13 volts with it revved up. Yes I have a DVM but's it's hard to watch while hooked to my battery and me driving the car.

Took my powermaster alt off my other car and put it on. Now I had over 14 volts at idle.

So I ordered another powermaster alt and put it on for good, now I have 15 volts and my car runs much better and idles smoother.

I know I should have put in a volt gauge when hooking up the #10 wire but didn't. At least now I know what my alt is putting out.

So my old 15 year old alt was still working, just not putting out like my old girlfriend used to.

So consider replacing your alternator. That's Daytona beach sand on the floor mat.