Voltage regulator plugged in backwards?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

kc69 · 10-02-2009, 04:46 PM

Would this damage the external regulator. I assuming that it would. I was only getting 12.4 volts back to the battery. Alternator was just check and it is good with 90 amps. So, I bought a new regulator, plugged it in like it had been (red wire 2nd one down from top), and still only 12.4 volts. I then unplugged it and turned it upside down (red wire now second from bottom), plug back in, and still only 12.4 volts. Did I "fry" it initially by plugging it in the wrong way? Oh, new battery too.

mclairmo · 10-02-2009, 05:03 PM

Was the engine on or off when you checked battery voltage?

chevy_mike · 10-02-2009, 05:28 PM

When I got my truck, it was rigged with a kill switch (household electrical switch at that) to kill all power to the truck. I found out why after leaving it on overnight. The battery was dead. Charged the battery but found I was having a large current draw that would only go away when this "kill" switch was turned off.

After poking around and stripping some wiring out, I found the PO had plugged the external regualtor in backwards. Doh!!!! Plugged it in the right way and my current draw went away and stopped killing the battery. Who knows how long it had been like that and putting back the way it should be, it worked fine. I doubt any damage was done to yours.

As asked, was the engine running or not when you checked the voltage. Running with the RPM's about 1300-1500, you should see around 13.5 +/- .5 volts depending on the charge of the battery. With the engine off or at idle, 12.4 would seem about right.

kc69 · 10-02-2009, 06:43 PM

My engine was running when checked. The battery won't stay charged because it's not getting enough juice back to it from the alternator-external regulator, only the 12.4 volts. Maybe I should just go get me a 1 wire alternator and be done with it...

ERASER5 · 10-02-2009, 08:14 PM

Bad idea. 1 wire alts suck at idle. If you are going to upgrade, just get an internal regulator alt. The swap is dead simple. If you are not big on electrical, there are simple plug in kits to be had. A 3 wire alt is always better than a 1 wire. Plus, standard 3 wire alts can be had at any auto parts counter in the USA.

kc69 · 10-02-2009, 08:30 PM

Hey, thanks for the advice on the 3 wire alternator...going to look into that

10-02-2009, 04:46 PM	#1
kc69 Registered User Join Date: Sep 2009 Location: Kansas city, Mo. Posts: 28	Voltage regulator plugged in backwards?? Would this damage the external regulator. I assuming that it would. I was only getting 12.4 volts back to the battery. Alternator was just check and it is good with 90 amps. So, I bought a new regulator, plugged it in like it had been (red wire 2nd one down from top), and still only 12.4 volts. I then unplugged it and turned it upside down (red wire now second from bottom), plug back in, and still only 12.4 volts. Did I "fry" it initially by plugging it in the wrong way? Oh, new battery too.

10-02-2009, 05:03 PM	#2
mclairmo Registered User Join Date: Jan 2006 Location: Take Off Posts: 1,908	Re: Voltage regulator plugged in backwards?? Was the engine on or off when you checked battery voltage?

10-02-2009, 05:28 PM	#3
chevy_mike Never Ending Projects Join Date: Jul 2006 Location: San Diego, CA Posts: 3,836	Re: Voltage regulator plugged in backwards?? When I got my truck, it was rigged with a kill switch (household electrical switch at that) to kill all power to the truck. I found out why after leaving it on overnight. The battery was dead. Charged the battery but found I was having a large current draw that would only go away when this "kill" switch was turned off. After poking around and stripping some wiring out, I found the PO had plugged the external regualtor in backwards. Doh!!!! Plugged it in the right way and my current draw went away and stopped killing the battery. Who knows how long it had been like that and putting back the way it should be, it worked fine. I doubt any damage was done to yours. As asked, was the engine running or not when you checked the voltage. Running with the RPM's about 1300-1500, you should see around 13.5 +/- .5 volts depending on the charge of the battery. With the engine off or at idle, 12.4 would seem about right. __________________ . 1965 C10 Panel, Tiki Express http://www.67-72chevytrucks.com/vboa...d.php?t=506580 SOLD 1968 Chevy C10, Long, Fleetside, Hot Rod Hauler http://67-72chevytrucks.com/vboard/s...d.php?t=313233 SOLD 1965 Chevy C10, Long, Fleetside, Hot Rod C10 http://67-72chevytrucks.com/vboard/s...d.php?t=415702 SOLD We were given two ears and one mouth for a reason... listen twice as much and speak half as often... Last edited by chevy_mike; 10-02-2009 at 05:28 PM.

10-02-2009, 06:43 PM	#4
kc69 Registered User Join Date: Sep 2009 Location: Kansas city, Mo. Posts: 28	Re: Voltage regulator plugged in backwards?? My engine was running when checked. The battery won't stay charged because it's not getting enough juice back to it from the alternator-external regulator, only the 12.4 volts. Maybe I should just go get me a 1 wire alternator and be done with it...

10-02-2009, 08:14 PM	#5
ERASER5 Registered User Join Date: Jun 2006 Location: Indiana Posts: 4,859	Re: Voltage regulator plugged in backwards?? Bad idea. 1 wire alts suck at idle. If you are going to upgrade, just get an internal regulator alt. The swap is dead simple. If you are not big on electrical, there are simple plug in kits to be had. A 3 wire alt is always better than a 1 wire. Plus, standard 3 wire alts can be had at any auto parts counter in the USA. __________________ '70 GMC C1500 LWB Power disc brakes. WooHoo! Posi 6 Lug Dana 60

10-02-2009, 08:30 PM	#6
kc69 Registered User Join Date: Sep 2009 Location: Kansas city, Mo. Posts: 28	Re: Voltage regulator plugged in backwards?? Hey, thanks for the advice on the 3 wire alternator...going to look into that



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