luckythirteen13

ive blown out 2 voltage regulators in the last few days and have no idea why. i have a 3g 150amp alt. i use a 2g wire to run from the alt to the battery that is in the trunk. the car runs fine. just after a short run the alt stops making power and when i check for the cause, its the regulator. i just installed my pms and am dying to get the thing tuned but my alt just keeps dying on me and its pissing me off.
the alt is out right now but just had it tested at pep boys after the new reg went in and it was making 14v no problems. i put my volt meter on my battery and it said 16v..wtf? took it to pep-boys and they tested that. came back as having just under 14v in it and passed with no problems. i plan to put my alt and sc back in tomorrow but am reluctant in fear of blowing the reg again. could the stock wires that plug into it be too old? ive had this alt on my car for about a year and no problems till just recently

90GTRagtop

Sorry, I'm not familiar with the 3g. Is it internally or externally regulated? If it's external, then the bench test will be using a different regulator and I would expect the votage to be OK cause that's what the regulator does. If it's internal, or if you're also using your regulator on the bench test, I'd start by making sure that everything has a very good ground. Also, if it's external, double check your wiring. If it's supplying 12V to the field for some reason, it will max out the alternator, thus the 16V you're seeing.

luckythirteen13

what field are you talking about? the reg is external.

90GTRagtop

If the regulator is external, I would expect it to have a conection labeled "field" among the wires. This supplies excitation voltage to the field windings in the alternator. More voltage to the windings generates more voltage to the battery, and the inverse is true also. That is how the regulator controls the voltage output of the alternator under differing loads, is to vary the field voltage. Thus, if an incorrect wiring is supplying 12V to the field, the alternator will be on max output. Another thing that can screw up this relationship is a bad ground. If the regulator is comparing to an incorrect reference voltage (as in when it's not grounded well), it can "think" the alternator voltage needs more adjustment in some direction than it really does. Make sure that both the regulator and the alternator are well grounded.

luckythirteen13

i have my battery in the back but the only ground i did from the battery is to the hatch area and thats it. i plan to go to the weld shop tomorrow and get some more 2g cable and run a ground from the stock location on the back of the driver's side head to the place where the battery used to sit (where i have the old negative battery cable grounded) and also plan to run a 10g wire right from the alt to the body on the passanger side. then i know it will be grounded....right?

90GTRagtop

Sounds like a good plan. Where is your regulator mounted? I'm assuming on the passenger side fender well from what you've said. I'm also assuming the battery old groung point you're talking about is to the engine block.

luckythirteen13

the regulator is on the alt attached to the back of it (does that make it not external? confused). the factory ground (the wire that used to be on the battery) is grounded to the body. i plan to run a 2g cable tomorrow from the back of the head to the same spot.