My 12 valve seems to over charge, at idle it charges to 15.1 to 15.3 volts, the amp gague bounces untill raised off idle. I am a dealer so I swapped inn a new not rebuilt altornator, and it does the same thing. I moved the VR to the fender well, and made sure all connections are clean, and grounded to the battery so the VR has a good ground. What else could be causing the gague bounce, and over charge?

Kasey

 

I can't tell you what's wrong, but I can tell you how to fix it.
What happens is, somewhere in the wiring to the voltage regulator there is resistance. This causes the regulator to "see" lower voltage than the rest of the system, causing the regulator to turn the field windings "on" when it really doesn't need to. The extra voltage overcomes the resistance and suddenly the regulator "sees" way to high of a voltage reading. This causes the pulsing you're seeing.
The way I overcame this, was to add a wire from the battery, to a relay, feeding the blue sense wire on the regulator. After doing this, the voltage gauge is rock-steady and I get a dvm reading of steady 14.4 volts.
I did have a problem when I did this at first. I used a hella relay without an internal suppression diode. Relays that don't have a suppression diode release a 300 to 500 volt short duration spike from the coil at very low amperage when turned off. This fried my regulator after the third time I shut the truck off. I put a relay in it with a suppression diode and it has been fine ever since.
Now, the best way would be to find the actual source of the voltage drop, but this is very simple way of overcoming the problem.

 

You are correct, it was a resistance issue, I found my ignition switch which is where the blue wire gets its key on power from, and the switch itself has a few melted terminals, and I just touched the blue wire, and the amp gauge mellowed out, and the volts went to 14.8 ish. So I ordered a new switch.

Kasey

 

The way I overcame this, was to add a wire from the battery, to a relay, feeding the blue sense wire on the regulator. After doing this, the voltage gauge is rock-steady and I get a dvm reading of steady 14.4 volts.

WOW! someone else did the relay thing too! I no longer feel like such a "freak" !

 

Can you give me some kind of wireing diagram to follow? so is it just a wire off the battery to a rellay tapped to the blue wire, what turns the relay on? Im no electrical genious so I need pictures ...

Kasey

 

Try this...

 

Is there a certain ize diode thats suposed to be in the relay? I have a relay with a diode inn it, but I dont know how heavy it should be. I am assuming that the diagram is like this,

Top is tab 30
left is tab 85
right is tab 86
bottom is tab 87

Correct?

Kasey

 

Wow, I wish I knew this about 8 years ago when I had my 89. I went through VR's like crazy trying to fix it and this would for sure have done it..

 

SWEET!! I hooked it up, and its VERY steady at 14.45-14.56 volts, when the A/C cycles its jumps to 14.56 then down to 14.45ish. Thanks Guys!!

KAsey