VOLTAGE REGULATOR PROBLEMS PERSIST **911/HELP**

[70 Grand Coupe]

I am stumped. I just installed a new VOLTAGE REGULATOR (VR). The alternator puts out 14.3V at idle but climbs up to 16-17V at high idle. My radio is cutting in and out and the voices in my head are getting louder  :bang head:.

For those of you that are just tuning in, I have been chasing this gremlin for a while in (2) previous threads. I thought I had it licked until I took the car for a road test and discovered the radio was cutting in and out.

- Initially, I thought the alternator was shot because the battery was dying and it was putting out 11.6V.
- Alternator was replaced and problem persisted, although new alternator was putting out 13.4V.
- Replaced VR with NOS from a 70 Grand Coupe.
- The new alternator was putting out 16+V at low idle.
- NOS VR swapped for new VR. Alternator putting out 16+V at battery.
- Replaced new alternator with original alternator I originally though was FUBAR, putting out 14.3V at idle. Did not check voltage output at high idle.
- During road test, radio began cutting in and out.
- Volt meter at battery shows 17V+ at high idle.
- Changed out new VR with another (I bought 2 cuz they're only $18 each). SAME THING. AT IDLE ALTERNATOR OUTPUT 14.3V, HIGH IDLE: 16-18V

I AM EXTREMELY CONFIDENT THAT I HAVE GOOD GROUNDS TO THE WHOLE CAR. I.E. I HAVE SEPARATE GROUNDS TO MARKER, SIGNAL AND TAIL LIGHTS WITH (2) BATTERY/CHASSIS GROUNDS, (1) ENGINE/CHASSIS GROUND.

YOUR ASSISTANCE IS GREATLY APPRECIATED.

Regards,

Darcy

 
 

[GoodysGotaCuda]

I've been down this road. If you aren't familiar with it already, your voltage regulator is going to be sensing voltage and varying the ground circuit to the alternator to vary its output. If you have -lower- than battery voltage going -to- the VR, it will try to over-compensate and apply unrestricted ground to the alternator. Over-charging the battery.


Put a voltmeter on the 12v+ wire going into the VR (there are only 2 pins) with the car running and compare it to the battery. What you are wanting is the same value, if it reads 16.0v at the battery, it better read 16.0v at the VR. If it reads 16.0v at the battery and 11.5v at the VR, you have an issue (that's slightly exaggerated). The issue would be a faulty connection or corrosion on that "sense" 12v wire on the voltage regulator, you will need to solve that.

If that reading is good, you then need to question the ground from the voltage regulator's case, to the chassis. There needs to be a good battery to body ground and the VR case needs to have a good connection to it.

So what if the voltage reading is low? You need to find the source of the problem, but you can by pass the original wiring, if you have to. What I ended up doing was putting the voltage regulator on a relay and letting the factory wire just trigger the relay. The relay provided solid battery voltage to the VR, with almost zero voltage drop. It solved my over-charging issue completely.


For a temporary "test" solution, you can use some hearty alligator clips to replicate the mentioned repair. Take the pin on the VR you sensed 12v+ on and tie it directly to the battery positive. Take the other pin on the VR and tie it to the respective pin on the wire harness. That will effectively "bypass" the factory gremlins in the wiring to the VR.  Run the car and record the results.

[HP_Cuda]

So for the VR's you are using, the case is actually the ground to the firewall.

When you utilize the correct bolts that will grab ahold of the firewall and then clamp the VR to the firewall causing a ground. If you can grab your VR while it's attached to the firewall and move it around you don't have a good ground.

The VR needs to be solidly and I mean solidly attached to the firewall creating its own ground. I had a very similar situation to yours, put in a new VR and had the same problem. I changed out the bolts to the correct ones and whammo - good ground and the VR worked as promised.

[YellowThumper]

The factory setup on my 74 has a ground strap that attaches one end with the vr mount screw and the other to the back side of the passenger side head.

[roadman5312]

So for the VR's you are using, the case is actually the ground to the firewall.

When you utilize the correct bolts that will grab ahold of the firewall and then clamp the VR to the firewall causing a ground. If you can grab your VR while it's attached to the firewall and move it around you don't have a good ground.

The VR needs to be solidly and I mean solidly attached to the firewall creating its own ground. I had a very similar situation to yours, put in a new VR and had the same problem. I changed out the bolts to the correct ones and whammo - good ground and the VR worked as promised.
[/quote
                    I always grind off the paint at 1 mounting point and add a ground wire to the engine. I'm an overgrounder 

[dodj]

I am stumped. I just installed a new VOLTAGE REGULATOR (VR). The alternator puts out 14.3V at idle but climbs up to 16-17V at high idle.

You have high resistance connections in your system. Take ALL connectors apart and clean them.

[70 Grand Coupe]

FIXED! It was a corroded SENSE 12V CONNECTOR to the VR that was the culprit. Whew! Was a real ***** to clean with the electrical connector cleaner......I had to scrape off the plug with upholstery hook several times.

FYI, I do have the proper bolts holding the VR to the firewall along with what I believe is to be the OEM ground strap to the VR and engine. Stereo is working properly at high RPMs so I didn't fry that either. 

I had it all ass backwards, Hind site is a *****: I should have immediately checked VR and connectors before changing out alternators x 2 and contemplating buying another car and selling this one  ........lol!

Thank you all again for your assistance. Y'all have been the best resource, thank god for this forum and the ol inter web! 


Kind Regards,

Darcy

 
.

[HP_Cuda]

 

[roadman5312]

                                           

[734406pk]

  This is a very common issue. That Dark Blue wire is used for regulator voltage sensing as well as the case ground. Any resistance on either side can cause overcharging. Having some spare regulators is not a bad thing... Good Luck with your car!

[GoodysGotaCuda]

Glad to hear it's sorted out.


Sent from my iPhone using Tapatalk

[Chryco Psycho]

using some di-electric grease on the contacts everywhere can help prevent this , do the bulkhead & column connections too

[HP_Cuda]

 

I did this across all of my connectors when I put the wiring harnesses in the front and rear of my green Cuda.