Basic Electrical Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Montana71 · 09-27-2002, 11:18 AM

Hey guys, long time no post but truck projects moving forward, anyway a question.

I have known for months that I had some electrical gremlins in the lights of my '71, and after working on some trailer lights last night I think my problem is an improper ground. Normally my taillights have been very dim, and the turn signals occasionally don't work. Well I was working on the connection between my truck and camper and realized that when I externally grounded the truck trailer plug to the bumper or the camper frame, that the truck lights worked alot better and brighter. So I must have a ground problem, could this failing ground be at one location or mutiple locations in the truck? Thanks for any thoughts...

adamls · 09-27-2002, 11:23 AM

Your trucks 30 years old. It is very possible the entire harness is going south.

71GMC_3/4T · 09-27-2002, 03:17 PM

I'd say you have a ground problem. Grab a voltmeter, turn on the lights and measure between things that *should* be at the same potential, i.e., ground. If you measure between the frame and bed and get 2 volts, you have a problem. Run a ground wire using star washers under the ring terminals from the frame to the bed. Keep looking. Measure engine block to fender with it running. Anywhere you get voltage between things that should be ground, you need to tie them together with a ground strap.
Also, check your taillight housings vs the bed. In a truck that's 30 years old, rust can build up between surfaces and create ground problems.

09-27-2002, 11:18 AM	#1
Montana71 Registered User Join Date: Sep 2000 Location: Kalispell, Montana Posts: 136	Basic Electrical Question Hey guys, long time no post but truck projects moving forward, anyway a question. I have known for months that I had some electrical gremlins in the lights of my '71, and after working on some trailer lights last night I think my problem is an improper ground. Normally my taillights have been very dim, and the turn signals occasionally don't work. Well I was working on the connection between my truck and camper and realized that when I externally grounded the truck trailer plug to the bumper or the camper frame, that the truck lights worked alot better and brighter. So I must have a ground problem, could this failing ground be at one location or mutiple locations in the truck? Thanks for any thoughts... __________________ 71 C10 LWB Cheyenne 68 C10 SWB parts truck "http://www.cenlog.com/71chevy.htm"

09-27-2002, 11:23 AM	#2
adamls Gotta Startem Early Join Date: Oct 2001 Location: Amarillo, TX, USA Posts: 364	Your trucks 30 years old. It is very possible the entire harness is going south. __________________ 67 SWB In Progress, one piece at a time, maybe 3 years I will be finished

09-27-2002, 03:17 PM	#3
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	I'd say you have a ground problem. Grab a voltmeter, turn on the lights and measure between things that should be at the same potential, i.e., ground. If you measure between the frame and bed and get 2 volts, you have a problem. Run a ground wire using star washers under the ring terminals from the frame to the bed. Keep looking. Measure engine block to fender with it running. Anywhere you get voltage between things that should be ground, you need to tie them together with a ground strap. Also, check your taillight housings vs the bed. In a truck that's 30 years old, rust can build up between surfaces and create ground problems. __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO



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