Overcharging issue - Voltage regulator to blame?

Posted By: Pat_Whalen

Overcharging issue - Voltage regulator to blame? - 10/16/10 04:44 AM

Haven't started delving into all of the possible problems, but I'd like some feedback on things to look into.

Truck starts up and, during an idle, will be feeding 12.5-13 volts to the battery.

Problem begins when I'm driving it around. Voltmeter (tested and good against a multimeter) climbs exponentially in relation to the RPMs I'm currently at. There seems to be no regulation on how much voltage the alternator is sending out. Cruising at 2000RPM, the voltmeter reads 17 volts and might actually be pegged. Haven't ran a voltmeter simultaneous to find out actual value. Just know that it's too high.

Does this sound like a bad voltage regulator? I haven't tried another one and I can't verify that this one is good. I do know that I've got a good ground at the regulator.

Thanks in advance.

Posted By: zrxkawboy

Re: Overcharging issue - Voltage regulator to blame? - 10/16/10 04:50 AM

Most any parts store can test your VR.

Posted By: Kern Dog

Re: Overcharging issue - Voltage regulator to blame? - 10/16/10 05:03 AM

Not at the Kragen/O Rielly or Auto Zone in my town. Maybe NAPA or CarQuest?
I have had Voltage Regulators give the symptoms you describe... overcharging. If you replace, save the trouble and buy a good one. They also need to be grounded. I once tested a pile of used VRs on a car and found that after several in a row tested bad, they were actually okay if I grounded them with a jumper wire. I was testing them while laying on the inner fender.

Posted By: RapidRobert

Re: Overcharging issue - Voltage regulator to blame? - 10/16/10 05:17 AM

Quote:

Does this sound like a bad voltage regulator?

Yes. I just had one ('70 up flat VR) suddenly start pegging as soon as I gave it throttle. Checked it's ground w a jumper wire w alligator clips/no change. R&R'd it & back to good. EDIT I would deal w it ASAP before it burns some wiring/connections & I'd unplug it rather than let it overcharge 'till you get it

Posted By: Pat_Whalen

Re: Overcharging issue - Voltage regulator to blame? - 10/16/10 07:38 AM

Quote:

Quote:

Does this sound like a bad voltage regulator?

Yes. I just had one ('70 up flat VR) suddenly start pegging as soon as I gave it throttle. Checked it's ground w a jumper wire w alligator clips/no change. R&R'd it & back to good. EDIT I would deal w it ASAP before it burns some wiring/connections & I'd unplug it rather than let it overcharge 'till you get it

So unplugging the VR will result in a no-charge state? Or just the standard 12.5-13V charge?

I'll take your guys word for it and slap a new voltage regulator on there. Like I said, I have no way of knowing that the one on there now is good. Although, I have no way of knowing that the foreign-made one I buy from Checker will be good either....

I'll keep my fingers crossed

Posted By: 1_WILD_RT

Re: Overcharging issue - Voltage regulator to blame? - 10/16/10 07:48 AM

Unplugging the V/R should disable the charging, if it doesn't than the problem isn't the regulator it's either a issue with the alternator or the green wire from the alternator to the regulator... The regulator grounds the field windings of the alternator through the green wire, the blue wire going to the alternator provides a switched 12v power supply to the field windings, the same blue wire also goes to the V/R providing a "sense" wire that the regulator samples to know the system voltage... So a bad ground or low voltage to the sensing wire at the regulator can cause over charging, a grounded green wire from the alternator to the regulator can cause overcharging or an internally grounded field winding in the alternator can cause overcharging..

Posted By: RapidRobert

Re: Overcharging issue - Voltage regulator to blame? - 10/16/10 02:43 PM

Quote:

So unplugging the VR will result in a no-charge state?

Yes & if it does not go to discharge then what 1 wild rt said it is a wiring prob (eyeball the brushes too) rather than the VR. I would pull the plug as that will be akin to leaving your lights on & draining the batt which is far less damaging than the full fielding that is happening right now w it.

Posted By: Pat_Whalen

Re: Overcharging issue - Voltage regulator to blame? - 10/17/10 02:47 AM

Thanks again for the help felluhs. As suspected originally, the voltage regulator took a crap. Installed one I had laying around (circa 1977) and the voltage is a steady 14.3 while cruising. It does dip a little lower (12.8) at idle, but as soon as I'm off idle, it picks right up. My idle is a little low at around 650 rpm in gear, so that might be why.

Thanks again