electrical issues, dimming lights, occasional stalling, rough idle at stop

[Evan Frucht]

I've been having issues with my electrical system since I bought the car. I didn't really suspect it was electrical until now but now I'm thinking various symptoms might be connected.

Main problem is a rough idle. Sometimes sort of coughing or stumbling, hesitating, erratic. It stays running most of the time so it is tolerable to drive but every once in a while it will stall while sitting in traffic, but will start up again. Every few times I drive it this happens. Especially once the car gets really warm or on a very hot day. It accelerates fine and drives well, has plenty of power and engine is smooth... its only at a stop light/sign, when idling in DRIVE that this happens. If I put it into NEUTRAL then it smooths out. Once I accelerate it smooths out. The idle is set to about 700rpm, I tried turning it up a bit but that didn't help.

Another symptom is that the headlights+all other lights dim significantly at idle. It's enough that I cant really make out what the gauges say because the instrument cluster lights dim so much.

With car off voltage reads 12.5v
The voltage at idle in drive with headlights on was at 10.5v
In neutral it was at about 11.5v-12v
When I revved the engine up it would go to about 13.5v-14.5v

I brought it into auto zone to have them do a free charging system check on my car and the guy told me the result of the test was that my voltage regulator was bad

...so I ordered a voltage regulator and installed it today but the problem is not any better. if anything it is worse. the headlights dim badly still and to make matters worse now when I rev the car the voltage reads 16v-17v (doesn't that mean my NEW voltage is bad) when before it topped out at 14.5 volts. also my ammeter moves more radically now.

I'm lost. I'm thinking of trying a new alternator (maybe its going bad?) and/or a new coil but at the same time I don't want to just throw parts at it.

any ideas?

any tests I can do with a multimeter to test the my new and old voltage regulator to see if the new one is defective or if the old one worked fine?

any tests I can do on the alternator or coil?

1964 Plymouth Fury w 318/727​

 

[bearman]

Has the car been updated and what type of ign system are you using. Have you ever bypassed the ammeter.

 

[Glenwood]

turn your idle up a bit and recheck the voltage, it is too low. Then take a careful look at your bulkhead connections unless you bypassed them for the alternator/ammeter as I have done. If the voltage is still too low at idle without a load applied, your alternator is likely weak or the replacement regulator isn't very good. I changed to a powermaster alt & later style reg on mine to support a cooling fan load at idle. Go through all of the ground/neg connection points carefully to make sure they are clean and have good contact with bare metal.

 

[matthon]

I had the same issues, but a 2 barrel.

Carb had a tiny piece of lint in it, member here told me exactly where to look, solved the stalling issue.

I have an msd ready to run, tested battery/alt, replaced both, replaced the vr with an electronic one, done.

Lastly, get the napa electronic flasher, stock was causing a draw of some kind, dash lights weren't very bright, left dash directional stayed on, voltage was a little low, solved all those issues.

I also previously bypassed my charge wire, ensured good grounds, connections, etc.

 

[HEMI-ITIS]

Test the voltage at the back of the alternator and the battery,let us know the difference. Start there and we can go through step by step.Is the stock amp gauge still in use??

 

[Evan Frucht]

The ignition system and charging system is stock. I'm honestly not sure I have the correct alternator though, it could be a later model but idk how to tell ?

The original ammeter is still connected and seems to be working

I cant turn up the idle enough to fix it without having a ridiculously fast idle

I'm pretty sure the stalling is an electrical issue related to the dimming lights, and not a problem with the carb

its almost feels like the distributor doesnt have a enough voltage to keep up or something

I have a little device which records voltage at the cigarette lighter. It reads 10.3 when idling in DRIVE and foot on brake, headlights dim and idle becomes rough and hesitates randomly or will skip a beat.

 

[Evan Frucht]

Test the voltage at the back of the alternator and the battery,let us know the difference. Start there and we can go through step by step.Is the stock amp gauge still in use??

ill check that with a multimeter and post the results

 

[Evan Frucht]

Test the voltage at the back of the alternator and the battery,let us know the difference. Start there and we can go through step by step.Is the stock amp gauge still in use??

the voltage at the battery while idling in PARK was about 15 volts
the voltage at the alternator terminals was fluctuating between about 7 and 9 volts

on a side note, the rpms are faster in NEUTRAL vs DRIVE (where my problems start)

 

[HEMI-ITIS]

OK,time to trace that power wire from the alternator to bulk head and check voltage on both sides,then volts going into Amp meter and coming out.That will keep you busy for an hour or so.........

 

[Evan Frucht]

OK,time to trace that power wire from the alternator to bulk head and check voltage on both sides,then volts going into Amp meter and coming out.That will keep you busy for an hour or so.........

I actually think I tested the alternator wrong. I attached both of the multimeter wires to both posts on the alternator and got the reading of 7-9v

when I attach the positive of the multimeter to the positive wire coming off alternator and attach ground of multimeter to ground on engine I get the same reading of 15v that I get off the battery?

what does that mean?

 

[HEMI-ITIS]

Positive to alternator ground to engine.

 

[Evan Frucht]

Positive to alternator ground to engine.

ok so I'm getting a reading of about 15v off the alternator at about 1000rpm when I'm idling in neutral

 

[Evan Frucht]

both sides of my ammeter are reading 15v as well

 

[HEMI-ITIS]

Check voltage to fuse box and ignition.The ignition switch could also be suspect........

 

[Evan Frucht]

The voltage at the fuse box and ignition switch is 15v as well

 

[Evan Frucht]

I'm wondering if maybe my alternator is going bad and not charging as well at lower rpms

 

[khryslerkid]

See what it's charging as you drop the rpm with the idle screw. Check with the lights on also.

 

[Evan Frucht]

See what it's charging as you drop the rpm with the idle screw. Check with the lights on also.

When I put it into DRIVE (which brings the rpm down) and step on the brakes, with headlights on, the voltage drops down to 10.5

 

[Evan Frucht]

I'm also wondering if this NEW Voltage regulator I just got is bad. It will go all the way to 17 volts when I rev it up fast. Isn't a voltage regulator supposed to keep it under 14.5? My old one seemed to work but the autozone charging test concluded it was the regulator. I'm wondering if I should go back to the parts store and return it or exchange it?

 

[HEMI-ITIS]

Everything sound right except going up to 17 volts.Try a new regulator and try again