What can cause a Voltage Regulator to die?

[Dean_T]

My '78 Fairmont just killed its third Voltage Regulator. When the Discharge idiot light went off the first time, I replaced the alternator (Carquest rebuild), voltage regulator (same place), and the battery (AC/Delco). After a few hours of driving, the second VR drop dead.

I installed a third VR (NAPA Eichlin thingy) and it went 10-7 after a few hours/hundreds of miles too. I had the alternator checked each time before installing another VR but it always passed.

I did check the alternator wiring harness for continuity and had to replace the stator terminal (must have been too rough removing it) but haven thought of checking for grounds.

Help!

Oh, stock '78 302 V8 Fairmont with Duraspark ignition - nothing fancy.

Thanks in advance.

Dean T

[TuxStang]

Grounds ... electronic voltage regulators require them good to last (grounds are the two bolts).

[jrc347]

I've seen more than my fair share of "problems" with aftermarket alternators. Check and clean all connections first, then try to get your hands on an oem replacement regulator. Good luck

[JACook]

I've also got a pretty low opinion of rebuilt alternators in general. If you're losing
regulators, I would suspect the alternator, or the wiring. A solid state regulator will
not tolerate intermittent shorts in the field circuit, and I have seen some rebuilt
alternators with shorted rotor windings. They can be difficult to diagnose because
they will check out fine on the bench, but will short once the rotor is spinning.

At the same time, carefully examine your wiring from alternator to regulator, paying
particular attention to the wire that's going to the 'FLD' terminal. Should be orange
with a light blue stripe. The field circuit is what usually kills regulators.

And do make sure the mounting bolts for the regulator are clean and tight. I don't
think this has much to do with them blowing out, but the regulator does need a
good ground reference in order to... regulate.

[Ltngdrvr]

Time for a 3G upgrade maybe?

[anthonydalrymple]

Time for a 3G upgrade maybe?

X2....

[JACook]

A 3G is nice, if you need the extra power, but IMO, a '78 Fairmont doesn't have
a big enough main power wire to take advantage of it. Sometimes there's nothing
wrong with just fixing what's broke...

[Dean_T]

Hi all,

Thanks for the info. The Fairmont wagon is just a parts chaser so I don't really want to modify it more than it is now.

I just rechecked the alternator to regulator wiring harness and it seems the field wiring goes open if I pull on both ends while performing a continuity check. I cut off the plastic cover off the alternator side of the Field wire terminal lug and it is solidly crimped to the wire and not broken. Crud, it's in the harness to the intermediate connector. I may have to perform a Bypass Surgery.

This would explain why it wouldn't charge but I'm not sure. I'll have to pop in the original and two replacement VRs and see if it charges or not. I also have another replacement VR to use. I wish the parts stores would stock Motorcraft parts...

I tried some Ohm reading tests on the reman alternator per the '78 Ford shop manual but the readings I got weren't anything like the shop manual dictates. It may have something to do with the particular digital VOM I'm using. They used an analogue unit.

Dean T

[LTDScott]

Have you pulled out your instrument cluster lately? I recall years ago I pulled mine out and didn't plug the connector back in fully and it caused my charging system to cause problems.

It's a long shot, but just trying to help.

[Skinney]

My old Capri used to give me similar problems, it ended up being my battery cables, replaced them and didn't have any problems after, the coating was split exposing the wire inside and it started to corode.

[red86]

My 86 has been giving me that problem for years. I've noticed it more so when I use my lights or when I fill the car with more than 3/4 of fuel. Matter of fact I've just changed the constant voltage regulator this morning for the unteen thousand time. I've change to higher volt alt., got ground everywhere and I still can't find the problem. Any help is welcome.

[Dean_T]

LTDSCOTT: Oh yeah, I did do a heater core replacement a few months back - plus the car does have a weird ground problem when the headlights are on. I'll have to recheck that connector.

SKINNY: Yeah, I had that problem with my '78 Friggin' Futura. Funny thing was it's charge light never lit up - it just didn't start one day...

Red86: Isn't electrical problems the beeech?! Good luck and hope you find out what it is (and please tell us!)

Dean T

[Mad Max]

My capri was doing something similar. Everything worked except the charge system. changed everything twice. Turns out to be the ignition switch was faulty.

[Dean_T]

Oh no, not another ignition switch! LOL!

The tumbler on the wagon is shot as it is, wouldn't surprise me if the switch is coming a part also. It's an easy check - thanks for sharing!

Dean T

[Dean_T]

Okay,

Before I got sick with a flu, I had bypassed the Field wire on the alternator harness. Wagon fired up and the Discharge light went out like normal. Drove the car for 30 minutes and the light didn't go back on! This is with the second VR I was using as well! I used the second VR only because it said "short circuit protected" like some of the Motorcraft VR's used to.

I think I fixed it... I'm going to go on a 1 hour wrecking yard run to test it further. No if I can just get well...

Dean T