Electrical "surging" - The 1947 - Present Chevrolet & GMC Truck Message Board Network

OregonNed · 01-28-2013, 10:56 PM

Today I started my truck and as it sat and idled, I noticed the heater fan, (which was on high) would occasionally speed up considerably- with a corresponding jump from a steady 12 volts or so on the ammeter to a "jumpy" 14-15 volts. Then by itself it would slow down again. I was just wondering if these surges might indicate a faulty alternator or voltage regulator. thanks!

Coley · 01-28-2013, 11:23 PM

Sounds like a regulator to me.
If you have a spare regulator ground it somewhere near the existing mounted (suspect) one and simply unplug the harness from the suspect unit and plug it into the 'test' one.
If the suspect regulator is faulty you will immediately notice the difference with the (good) test unit.
(note: thats why its always good to find/get/use any spare electrical stuff when you get a chance....makes for quick, easy and cheap troubleshooting).
Good Luck, keep us posted.
Coley

71swb4x4 · 01-28-2013, 11:30 PM

I agree with Coley. When I read the title I thought regulator immediately, without reading anything else.

gangforward · 01-29-2013, 12:18 AM

Had problems similar to this, and replacing the regulator etc helped, but didn't solve the problem. Finally pulled out the DVM and tested a bunch of stuff, and found the 40 plus year old wiring was a big part of the problem. Was not able to do a complete rewire, but did replace most of it, and it not only solved the problem, it made a huge difference overall.

Good luck!

OregonNed · 01-29-2013, 12:31 AM

Thanks for the advice. I haven't had the truck long. I bought it the first week of last December. Since then I haven't driven it much - been waiting for Oregon to get the title corrected for a typo on the VIN number so I can get it licensed. On the long drive home, I had issues with dimming lights and very slow wiper action. A loose / somewhat corroded positive battery connection immediately fixed all the lights, but didn't correct the wipers. It took some time to hear and see the heater fan fluctuation, so hopefully these two issues might be related. The grounds look good, but I haven't inspected too much of the wiring, however.
Posted via Mobile Device

01-28-2013, 10:56 PM	#1
OregonNed Registered User Join Date: Dec 2012 Location: Vancouver, Washington Posts: 1,644	Electrical "surging" Today I started my truck and as it sat and idled, I noticed the heater fan, (which was on high) would occasionally speed up considerably- with a corresponding jump from a steady 12 volts or so on the ammeter to a "jumpy" 14-15 volts. Then by itself it would slow down again. I was just wondering if these surges might indicate a faulty alternator or voltage regulator. thanks! __________________ 1968 Chevrolet C/10 LWB - 327, TH350 - 4/5 Drop

01-28-2013, 11:23 PM	#2
Coley Registered User Join Date: Oct 2011 Location: Victoria, B.C Posts: 3,794	Re: Electrical "surging" Sounds like a regulator to me. If you have a spare regulator ground it somewhere near the existing mounted (suspect) one and simply unplug the harness from the suspect unit and plug it into the 'test' one. If the suspect regulator is faulty you will immediately notice the difference with the (good) test unit. (note: thats why its always good to find/get/use any spare electrical stuff when you get a chance....makes for quick, easy and cheap troubleshooting). Good Luck, keep us posted. Coley __________________ ....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL 1966 Chevy 1/2 ton (Florida- Red/white) 1972 Chevy 1/2 ton (California- Blue/white) 2005 Chevy Silverado HD2500/Duramax 2000 Dodge Ram 1500

01-28-2013, 11:30 PM	#3
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	Re: Electrical "surging" I agree with Coley. When I read the title I thought regulator immediately, without reading anything else. __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

01-29-2013, 12:18 AM	#4
gangforward Hootis is as Hootis does... Join Date: Nov 2002 Location: Southern Georgia Posts: 500	Re: Electrical "surging" Had problems similar to this, and replacing the regulator etc helped, but didn't solve the problem. Finally pulled out the DVM and tested a bunch of stuff, and found the 40 plus year old wiring was a big part of the problem. Was not able to do a complete rewire, but did replace most of it, and it not only solved the problem, it made a huge difference overall. Good luck! __________________ 67 C10 LWB Fleet, 383, TH400, PS, 4BL-Holley, Headers & 3" Exhaust, 3" drop front, 4" rear springs, ECI shock relocate, Panhard Bar kit, wheels & tires 1995 Z28 Convertible - Borla, K&N, Lingenfelter Motor, C6 Wheels & Tires 1990 2500 4x4 Suburban 3" Catbac System, K&N, 2" Lift, Wheels, Tires

01-29-2013, 12:31 AM	#5
OregonNed Registered User Join Date: Dec 2012 Location: Vancouver, Washington Posts: 1,644	Re: Electrical "surging" Thanks for the advice. I haven't had the truck long. I bought it the first week of last December. Since then I haven't driven it much - been waiting for Oregon to get the title corrected for a typo on the VIN number so I can get it licensed. On the long drive home, I had issues with dimming lights and very slow wiper action. A loose / somewhat corroded positive battery connection immediately fixed all the lights, but didn't correct the wipers. It took some time to hear and see the heater fan fluctuation, so hopefully these two issues might be related. The grounds look good, but I haven't inspected too much of the wiring, however. Posted via Mobile Device __________________ 1968 Chevrolet C/10 LWB - 327, TH350 - 4/5 Drop



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