Another bad voltage regulator?

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Went and got a replacement chinese Vr and now the voltage is holding steady at 15.7v under all conditions. I let it get up to temperature and it got closer to 15.6v.
The power difference from battery to the Vr connector is about 1.2v lower than it should be. So I’m assuming that’s why the alternator is now putting out about 1.2v higher than it should.
Now to solve the harness drop.
 
After digging around the wiring for a while I don’t see any major issues with anything. I don’t feel like removing the factory “loom” from everything so I think I’m going to install a relay to give the Vr the true battery voltage it needs. Does it matter which pin on the Vr gets the full battery power? Both wires in the Vr connector have about 1v less than the battery when the engine is not running.
 
Absolutely. It matters. The two field connections at the alternator can be reversed.

altwir1-jpg.jpg
 
To clairify what 67dart said the wires ( power source) INTO the VR must be correct.

The wires going into the alternator can be either way.

In the older single field wire (not isolated field) alternators, the regulator regulates the 12v input to the alternators field wire to increase and decrease the field strength thus regulating the output voltage of the alternator depending on load.

The new style 2 field wire (Isolated field) regulator regulates the ground to increase and decrease the field strength thus regulating the output voltage of the alternator depending on load. Because it is an electronic regulator it needs a 12v source to run its electronics.
 
^^YUP^^ This had to do with transistors in the day. It was much easier to put the transistor in the ground leg, and even now, most aftermarket EFI seems to control pretty much any output in the ground leg
 
67Dart273 said:
^^YUP^^ This had to do with transistors in the day. It was much easier to put the transistor in the ground leg, and even now, most aftermarket EFI seems to control pretty much any output in the ground leg
Click to expand...
Yeah that’s how the Sniper system in my Duster controls everything too. Really made me realize how important grounds are haha
 
I haven’t gotten a relay yet, but figured I’d hotwire it before I wasted the money. I ran an 8ga wire straight from the battery to the connector of the Vr. Battery voltage is now holding steady at 14.7v
The voltage at the alternator output stud is 15.1v
I’ll take it.
Thank you for everyone’s input
 
Yeh you are headed there. As I keep harping LOL the ground at the VR flange MUST be same as battery neg and the VR IGN terminal MUST be same as battery POS. That is really the secret of the whole deal

"In part" that is why I caution against "one wire" alternators. They are OK if the charge wire--which is the sense wire--is oversized enough to keep sensing correct. A separate sense wire is by far better
 
67Dart273 said:
Yeh you are headed there. As I keep harping LOL the ground at the VR flange MUST be same as battery neg and the VR IGN terminal MUST be same as battery POS. That is really the secret of the whole deal

"In part" that is why I caution against "one wire" alternators. They are OK if the charge wire--which is the sense wire--is oversized enough to keep sensing correct. A separate sense wire is by far better
Click to expand...
When I install the relay, I’ll run an extra ground wire to the battery neg just to be safe.
This is probably the issue I was having with the externally regulated alts I was fighting with on my Duster. It now has a Chevy style one wire alt with a 4ga charge wire. It’s worked flawlessly so far.
 
4 thoughts...
I once swapped a /6 in a 79 D100, motor swung while hanging on cherry picker once broke loose from trans, VC smacked regulator, did something to the connector.... had same problem with it as you describe until I cut the pigtail and replaced it (for the regulator)

Ive had bad batteries cause alternator to go full tilt....

My son has had VR problems on a 72 Fury wagon and an 89 Ramcharger this year, went thru several VRs from parts store.... I went and dug up a couple of new but old Niehoff brand VRs from my stash, probably 40+ years old but brand new.... problem solved on both. good, new, OLD from a reputable brand.

on my 85 D150 I had issue with the regulator too.... wound up going junking and pulling a couple from junkyard refugees (my son used up my stash haha) put a used original VR on and works fine. I have been putting more junkyard parts on my vehicles the last few years and have bene having bette luck getting good parts vs buying Chinesium from the parts stores
 
I finally got around to installing the relay. I now have exact battery voltage at the VR, and the charging voltage is staying dead on 14.7 volts when measured from the battery. Problem solved!
Thanks guys.
 
Very good. I hope you don't lose any more VR's. If so, only suspect I could think of would be a field winding drawing too much current.
 
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