Voltage regulator issues

[Trey Osborne]

My car is a 1963 Plymouth valiant with a 1978 aspen engine, harness, alternator, and voltage regulator. The amp gauge works fine, but at anything over 2k rpm it goes all the way to the max, so I replaced the voltage regulator. That didn't change anything. I tried running a wire straight from the battery negative to the body of the regulator that also did nothing. If I unplug the regulator the car still charges, and at the same rate. What should I do?

 

[Mattax]

My car is a 1963 Plymouth valiant with a 1978 aspen engine, harness, alternator, and voltage regulator. The amp gauge works fine, but at anything over 2k rpm it goes all the way to the max, so I replaced the voltage regulator.

By max I assume you mean it shows maximum to the Charging side.
One possibility is the battery is very low or has an internal problem.
Put the battery on a charger. Slow charge (2 amps) if its not an automatically controlled charger. If its a traditional battery, check the acid level is over the lead plates. If not add some distilled water. Do this before connecting the charger.

Another possibility is a regulation issue.
Do you have a hand hand multimeter?
If so, a quick check is to measure the battery voltage across the terminals.
Do this engine off, then engine running at slow idle, and engine running at fast idle or something fast.

Engine off, no lights on etc, the battery should be close to 12.8 Volts.

Engine running voltage should be between 13.9 and 14.7 Volts.
Voltage may increase a little with rpms above idle but then should be the same whether its running at 1700 or 2000 rpm. And it should not be above 14.9 Volts.

 

[Trey Osborne]

By max I assume you mean it shows maximum to the Charging side.
One possibility is the battery is very low or has an internal problem.
Put the battery on a charger. Slow charge (2 amps) if its not an automatically controlled charger. If its a traditional battery, check the acid level is over the lead plates. If not add some distilled water. Do this before connecting the charger.

Another possibility is a regulation issue.
Do you have a hand hand multimeter?
If so, a quick check is to measure the battery voltage across the terminals.
Do this engine off, then engine running at slow idle, and engine running at fast idle or something fast.

Engine off, no lights on etc, the battery should be close to 12.8 Volts.

Engine running voltage should be between 13.9 and 14.7 Volts.
Voltage may increase a little with rpms above idle but then should be the same whether its running at 1700 or 2000 rpm. And it should not be above 14.9 Volts.

Yes I mean max charging side. Battery has been ran super low before, and boiled. (I had this issue and had to get home, went from disconnecting alternator to reconnecting to get home). I just bought another regulator, no change. I do have a multimeter and battery voltage reads 18 when I rev it. Is there some way I can test and see how it’s bypassing the regulator?

 

[Mattax]

I do have a multimeter and battery voltage reads 18 when I rev it. Is there some way I can test and see how it’s bypassing the regulator?

[edit.]

Something is grounding the field brush that connects to the voltage regulator (using the green wire).
> Test this one first. Engine off, key off, set the multimeter to resistance. Backprobe the field connection with one probe and connect the other with ground. The alternator housing or a mounting bolt is fine.
+> It should be open, infinate resistance, no connection.
- > If there is low or some resistance then disconnect the connector with the green wire. Restest by measuring resistance between the field terminal and ground. Then measure resistance between the green wire terminal and ground.

The "isolated field" alternator and regulator work by controlling the current flow to ground. There's a diagram in this post about 1/2 way down. So if there is a connection to ground before the regulator, the rotor will draw as much current as it wants without regulation.

 

[67Dart273]

EDIT:!!! IGNORE THE SECOND PART BELOW

I missed the part you say "you can unplug the regulator and it still charges." You have something wrong either in alternator or a harness wiring short. Unplug the green field wire at the ALTERNATOR and see if problem still exists.

WHAT do you have for a system? IS this the older so called "single field" (grounded field) Mopar unit, or "something else?"

======================================================================

EDIT IGNORE THIS FOR NOW
FIRST thing to do is confirm the battery is good or bad, or charged or not. Charge it have it tested. Then with the car running and with "it" able to show the problem, monitor battery voltage and see where it goes. If charging voltage is much above 15V you have a charging problem, likely. If voltage is below 15 most likely is a battery problem. You can also temporary swap in another good battery

MAKE CERTAIN REGULATOR IS GROUNDED. This is INCREDIBLY important. How to check: Run car, warm battery 'as normal" as you can get it, and run at fast idle to simulate "low to medium cruise" RPM

Run this test with all accessories off, and again with lights, heater, etc powered on.

Stab one probe of your meter into the battery NEG post and the other into the mounting flange of the VR. Make SURE to get through paint, rust, etc. You are hoping for a VERY low voltage, better yet ZERO, the lower the better.

If you read much of anything, above .3V (3/10 of one volt) check/ recheck regulator grounding to firewall, and ADD A GROUND CABLE between engine and firewall

 

[Mattax]

I missed the part you say "you can unplug the regulator and it still charges."

I missed that too!

 

[Trey Osborne]

EDIT:!!! IGNORE THE SECOND PART BELOW

I missed the part you say "you can unplug the regulator and it still charges." You have something wrong either in alternator or a harness wiring short. Unplug the green field wire at the ALTERNATOR and see if problem still exists.

WHAT do you have for a system? IS this the older so called "single field" (grounded field) Mopar unit, or "something else?"

======================================================================

EDIT IGNORE THIS FOR NOW
FIRST thing to do is confirm the battery is good or bad, or charged or not. Charge it have it tested. Then with the car running and with "it" able to show the problem, monitor battery voltage and see where it goes. If charging voltage is much above 15V you have a charging problem, likely. If voltage is below 15 most likely is a battery problem. You can also temporary swap in another good battery

MAKE CERTAIN REGULATOR IS GROUNDED. This is INCREDIBLY important. How to check: Run car, warm battery 'as normal" as you can get it, and run at fast idle to simulate "low to medium cruise" RPM

Run this test with all accessories off, and again with lights, heater, etc powered on.

Stab one probe of your meter into the battery NEG post and the other into the mounting flange of the VR. Make SURE to get through paint, rust, etc. You are hoping for a VERY low voltage, better yet ZERO, the lower the better.

If you read much of anything, above .3V (3/10 of one volt) check/ recheck regulator grounding to firewall, and ADD A GROUND CABLE between engine and firewall

I think I figured it out, I put bushes in alternator around 4 months ago, the little isolator that keeps the brush from grounding to the body of alternator is gone. I believe I probably overtightened it and broke the isolator as it is no longer there. I will reply again when I get a new one and can confirm this is the issue

 

[Mattax]

I think I figured it out, I put bushes in alternator around 4 months ago, the little isolator that keeps the brush from grounding to the body of alternator is gone. I believe I probably overtightened it and broke the isolator as it is no longer there. I will reply again when I get a new one and can confirm this is the issue

Yes the plastic insulator and the insulating washers are critical.

 

[67Dart273]

I think I figured it out, I put bushes in alternator around 4 months ago, the little isolator that keeps the brush from grounding to the body of alternator is gone. I believe I probably overtightened it and broke the isolator as it is no longer there. I will reply again when I get a new one and can confirm this is the issue

This happens a LOT way TOO much and it happens with "rebuilts" You have a 50-50 chance of burning up the wiring harness, because "if you happen" to reverse the two field leads, the blue switched ignition "run" feeding one brush is a dead short to ground

 

[Trey Osborne]

This happens a LOT way TOO much and it happens with "rebuilts" You have a 50-50 chance of burning up the wiring harness, because "if you happen" to reverse the two field leads, the blue switched ignition "run" feeding one brush is a dead short to ground

Thank you all for the help I appreciate it. Its all fixed now, I just installed a reman alternator instead of waiting for parts to fix old one, still will keep it in case if this reman ends up being junk. I've put a few hundred miles on it now with no issues.