Voltage Regultor Question

[superdart]

OK, I installed an FBO ignition, and it pretty much went off without a hitch.

But, It seems that somewhere along the line I smoked my Mopar voltage regultor. It charges at 12.8 at idle, but it runs up to 15 VDC when you rev it above 1500 RPMS.

It was an almost new regulator. Should I just get another unit? Is there a better one on the market? Is there something else that would cause this?

Everything else seems to work fine. It's a 3 wire 100 amp alternator.

[cutting torch]

It sounds like you may have a bad ground at your voltage reg. If this is happening, the reg. thinks the voltage is low, so it sends too much current to the field of the alternator, making it put out too much voltage.

torch

get a powermaster altenator withthe bult in regulator

[cutting torch]

I disagree... Don't throw parts at it, FIX it!!!

torch

[ehostler]

The original MOPAR setup (with upgraded alt) is a good system. It's either a faulty ground at the regulator, or the regulator has failed.

Why use an over priced powermaster. A GM 1 wire setup is less expensive and can be replaced at your local auto parts store.

[superdart]

Well, I already have a nice 100 amp that replaced my old 60 amper...

Sounds like the ground might very well be the problem. I'll look into that before I replace the regulator.

[superdart]

OK. I grounded the snot out of the regulator. I also ran an extra 10AWG wire from the alternator to the battery post of the starter relay (with correct fusible link).

I also took a minute to ballpark the timing a bit. At idle (900 RPMs) I'm running 15.94 vdc at the battery (and alternator).

Resistance through the field wires from the regulator to the alternator is negligable.

Just for kicks. Does anyone know if you can measure base resistance of the regultor across the contacts? I did, and got 2.5 mega ohms (this number does me little good since I don't know the circuitry of the regulator).

I guess I'll need to get a new regulator. I can't think of anything else that would cause high voltage.

When the car is running, the rest of the electrical system seems fine.

[cutting torch]

Just thought of another possible problem. Check continuity between ground and your field leads with the voltage regulator disconnected. You should not have any continuity. The three wires on the regulator work as follows: one wire is ignition switched power to the regulator, one is power to one field terminal, the last is regulated ground to the other field terminal. If that last wire is shorted to ground, it will put full battery voltage to the field. If this happens, the alternator will as much voltage as RPM will allow. That may be why it's ok at idle, but not at higher RPM.

torch

[John Kunkel]

I agree with torch, the most common cause of runaway voltage is a shorted field wire (usually green in color) between the alternator and the regulator. Along the valve cover is a common place to short out.

[superdart]

Well, it may be shorted, but not on the valve cover, because I reran the wiring along the fender, and it's in wire loom. I'll have to check elsewhere for a short.

[superdart]

OK - The green field wire is not grounding on anything.

The blue ignition wire (field 2) is grounding out on my electric choke. I disconnected it and started the car, no effect.

I'm running out of ideas. I guess it's time to get a regulator (didn't I say that a few posts ago)

I double checked my wiring for the ballast also. My car is wierd. The wire goes to from the ballast into a 4 way splice. 1 to the coil, 1 to the bulkhead connector, and 1 into a relay right underneath the ECU. Also, the yellow wire form the starter relay goes to this relay also. What is this thing? I don't have the factory service manuals yet, and Haynes doesn't even acknowledge it exsists.

I doubt it's the source of my trouble, but I'll rip it out if I can.

[John Kunkel]

Before springing for a new regulator, disconnect the green field wire (leave the blue connected) and see if the overvolt persists. If it still overvolts with the green wire off, the alternator field is shorted internally.

[cutting torch]

Good one, John. I didn't think of that one. That gives me another idea, though. If this is a used alternator, someone may have intentionally grounded one field terminal to use it with a mechanical voltage regulator.

Superdart, check to see if both field terminals have the insulating washers in them, and check for continuity to ground at both of them too.

torch

[superdart]

The terminals have already been checked. Both are isolater from ground. The alternator is (was?) good. It was the orignal 65 amp that I had rebuilt. It is 3 years old, but has only been run a few hours. I'll pull the green wire and see what happens.

The search continues...

Thanks

[superdart]

Pulled the field wire and the voltage immediately dropped from 15.8 to 12.1..looks like I found the culprit..good thing, since I already ordered a new one.

I have to swing by the dealer today to pick it up.


Now, does anyone know what that relay looking thing is? I've ordere manuals, but they're not here yet.

[ehostler]

It could be the regulator or it could be the field lead. If it has worn and is grounding somewhere (normally along the valve cover), then you will get the same indications.

If you pull the connector off at the regulator, does the voltage drop down or stay up?