Why am i blowing voltage regulators?

[problemaddict]

Is there a common cause of blowing voltage regulators? This is the second one. I've got an old-school style external regualtor wired right to the posts on the alternator. I haven't disconnected the internal, original regulator (it obviously doesn't work either).

THe last one was working great in the driveway. Idling, revving, heating up and cooling off. No voltage problems. Took it for a maiden test run around the block and within minutes, the volts were spiked up past 19v.

Picked up a couple more regulators from the junkyard and tried again tonight. W/ the new regulator everything was fine again at idle in the driveway. Took it for a test run again and same thing, within a couple minutes of driving, this regulator failed and voltage spiked.

I tried to hook up my last junkyard regulator, but got no change, so its possible that one was already bad...

any help would be much appreciated.

thanks

Mike

[mark]

im going to guess on this. I'm r/c motors when the brushes arc it messes a lot of things up, how are the brushes on your alternator?

[shadow88]

If you're getting high voltage output, it could be the alternator. This had me stumped before as well.

[turbovanman²]

Try a new reg and make sure the case is grounded properly! If there grounded and you blow another one, then without proper testing equipment, a good guess would be as mentioned, bad alt.

Heres a diagram-

[JDAWG]

I assume you dont still have the wire from computer hooked up right? Buying used stuff is hit or miss. I still have people come in and buy those old regulators, they dont last forever. Bu seeing as you have tried 3 I would say take the alt off and take it somewhere and have it tested.

[problemaddict]

I assume you dont still have the wire from computer hooked up right?

I didn't cut any wires to/from the computer, so yeah the stock wiring is still intact. I figured if the computer has already failed in the open position, it wouldn't matter... does it?

And i'll be taking the alt. to a store for testing this weekend.

Thanks for the suggestions!

-Mike

[JDAWG]

Get the alt tested and I would unhook any of the factory feild wires just incase (the 2 little wires).

[turbovanman²]

I didn't cut any wires to/from the computer, so yeah the stock wiring is still intact. I figured if the computer has already failed in the open position, it wouldn't matter... does it?

And i'll be taking the alt. to a store for testing this weekend.

Thanks for the suggestions!

-Mike

You can't have the computer and an external reg working together, its one or the other.

[paisley_pirate]

+1 on the alternator having a ground fault inside.

They may or may not catch it at the parts store (although the new testers are much better than years ago when I was turning wrenches) but a good alt/gen/starter shop should be able to.

Back in the Day, my 86 GLH-T did it when it only had 7000 miles on it (in 86) took the dealer 5 tries to figure it out... I kept telling them, replace the friggin alt, they kept checking it on their (archaic by todays standards) tester and saying, naw it's the computer, the alt is putting out plenty... so it was...

[Anonymous_User]

I had issues before and the ground going to the alternator had a bad connection. With the rubber mounts, this is critical. I ended up running a heavy gauge dedicated ground from the battery to the alt.