Electrical ?
 

What is the procedure for checking to make sure i have a ground connection on this truck.

where at and for what ? there are lots of ground straps on the truck, starting at the neg cable being attaches to engine, and engine attached to firewall and cab mounts attached to frame and so forth

What are your symptoms?

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1971 C10 swb stepside 350/700R4/3.73posi
Killingworth, Connecticut

Rear lights work until i apply the brake, then the passenger side rear goes out. I've checked bulb and socket no luck. What readings should i have at the socket where the rear harness connects, i'm hoping i can isolate it to the rear harness.

If all your grounds (socket to housing, housing to bed, bed to frame, etc) are in good condition, you may have a problem within your signal switch. Does the emergency flashers light up both rear lights? If so, I beleive it's your signal switch at fault, if not, check your wiring harness and plug connections for broken, pinched and/or corroded areas.

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1971 C10 swb stepside 350/700R4/3.73posi
Killingworth, Connecticut

I had a similar problem with my brake lights. I could get my tail lights to work but no brake or turn signals. I studied the electrical diagram for four days to see where I needed to check. Took out my steering wheel thinking it might be in the signal switch. Then took out the dash cluster and found out one of the light sockets to dash was gone. It just happened to be the one that was in the circuit for the brake and turn signals. Put in new socket and now everything works fine. Hope this might help. I would check to make sure all sockets are tight.

My vote is it'll be in the column. True, it's a guess, but thats where they always seem to be.
If it were a ground, you would have no lights back there. To confirm it though, just rin a long wire straight from the neg term of the battery to the tail light bucket and bolt it on. Then check if the light works.

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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
Need to pick up the one ton Longhorn with a PONTIAC 350/350soon.
Thanks every one!:)
Check out The Longhorn Webite.
If you need a pic posted, E-mail me at longhornmail@yahoo.com
Andy, in Columbus Ohio

I pulled the lenses off the rear lights and was looking at the bulbs. I noticed when the lights were on the brighter filament in the bulb on the driver side was on, which i think is normal, but on the passenger side only the dimmer filament was on. Then when i hit the brakes i loose the passenger side totally. It was almost like the contacts were reversed on the passenger side, so i rev. them no change. I am at a loss here. Anyone know where i should start, i hate to just start replacing things. Thanks

You have a bad ground in one or both of your taillight housings.
Pull the lens caps off, then remove the housings. Clean any rust off the mating surfaces. When you put them back together, see if you can get an external tooth star washer at the mating surfaces.
If this doesn't work, maybe you have a whole bedside that is making poor contact. In that case, I would run a wire from the taillight housing chassis down to the frame.
Also, clean your bulb sockets with a wire brush. You can get one that's almost perfect for the job at the hardware store. Buy the one for cleaning copper fittings for sweat soldering. Make sure the lights are off when you clean them and blow out any debris with compressed air.

i pulled the bed off some time ago and did not notice a ground strap on it. I didn't think the lights would work at all if it wasn't grounded. (I'm asking, I don't have a clue)I will try and clean up the fixtures and put a star washer in place. Where would you install a groung strap from the bed. Thanks

Your right, you would have no light at all. It is not your ground, it is a short somewhere.

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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
Need to pick up the one ton Longhorn with a PONTIAC 350/350soon.
Thanks every one!:)
Check out The Longhorn Webite.
If you need a pic posted, E-mail me at longhornmail@yahoo.com
Andy, in Columbus Ohio

Nichboy, What part of the city are you in?

Oklahoma City, Oklahoma.

Actually the light would work without a ground. It would follow the path of least resistance which would be back through one of the other lamp circuits. The other lights may or may not light up, depending how much current was flowing. This is a common problem.
Get some alligator clip jumper wires from the local radio shack. Connect to the lamp holder metal shell and the frame for ground. The lights will work, I'll bet, provided your bulbs are installed correctly and they're good. Then you need to figure out which ground was missing before and correct it.

I used to have the same exact problem with a semi truck I used to own, the problem was the trailer ground to the 5th wheel, everytime I'd use the brakes, I'd loose my brake lights and turn signals. I just ran a jumper wire from the trailer to the frame rail of the Pete. Worked great. Just make up a long jumper wire with an alligator clip on both ends, connect your taillight housing to the frame and check it out to see if it works.

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'72 Chevy 1/2T 4x4 shortbox stepside 350/350auto on '84
ralleys and 31/10.5s

67 Cutlass convertible
330, 3spd stick

90 GMC Jimmy
350/auto
Chad Stephens
Orleans,NE

If the description was that the dimmer fillimant light up without the parking lights on when the brakes were aplied, then I'd agree 100%. Plus, the bulb works when the turn signal is on, therefor, it is grounding and producing the light on the bright fillimant.
The brake/turn wire goes all the way into the cab as one, 3 wires for the red lenses run the chassis.
Yellow and brown for the driver's side light, Dark green and brown for the passenger side. The yellow is left turn sig/left brake, and the dark green is passenger turn and passenger brake. The brown wire travels the chassis as a single wire, goes to the drivers side light, and comes back out, traveling to the passenger side for the passenger parking light.
If there is only one wire going to the brake/turn, and the turn signal works, that will eliminate all possabilitys of being a bad ground, or a short in the wire along the whole chassis. This whole harness plugs in thust to the right(passenger side) and a little lower than the master cylinder.
So we just eliminated the whole outside of cab, and along the chassis.
Ince inside the cab is where I get a little fuzzy about the herness, I knoe the wires go up through the 1/2 moon connector into the stearing column, and back out. (working from the tailights up to the switched) and in the column is where the brake lights and the turnsignals combine. The brake lights, coming off the light switch is an orange wire going in, (full hot) and white coming out(hot when foot is on brake). The white wire goes behind the fuse box, and then up into the main cab harness, and into the 1/2 moon connector, where on the other side of the connector id comes out as black, and up into the harness into the turn signal switch, where it is split into a left light and right light.
I have troubleshot the brake lights on 4 trucks, and only once was it a bad ground, and it did nothing like this fault. I Understand the path of less resistance, but with the turn signal working, that proves that the ground is good.


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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
Need to pick up the one ton Longhorn with a PONTIAC 350/350soon.
Thanks every one!:)
Check out The Longhorn Webite.
If you need a pic posted, E-mail me at longhornmail@yahoo.com
Andy, in Columbus Ohio

Ouch. I just got a headache trying to read longhornmail's post! j/k http://67-72chevytrucks.com/board/ubbhtml/smile.gif

I just got my back-up lights to work on saturday, but not before I "regrounded" the entire back of the truck. I noticed a couple of things when I had everything apart:

1. The driver's side tail light housing is grounded, but the passenger side can light up without a ground. Probably because it either gets its ground from the driver's side, or somewhere else.

2. You can easily screw up and put the bulb in backwards, which is stupid I know, but what will result is a brighter-than-hell bulb (because it lights up the brake filament) but not expected results when you hit the brake.

3. Since we're working with a 12v system you should be able to get ~12v (usually 10.8 - 11.5v) drop between the power side of every light on the truck to a steady ground.

That's how I found out my ground problem. I placed the positive side (red) of a multi-tester (set to DC mV=) inside the socket and the negative (black) to a bare spot on the frame. I got the right voltage described above. I kept moving the negative probe to different spots on the rear bed panel until I reached the actual reverse light hole, and found out the reverse light housing DID have a ground, but the copper sleeve inside the socket DIDN'T!

I had to unplug the housing, and clean the hell out of it. The copper sleeve wasn't contacting the metal housing it was pressed into. Pain in the a$$, but I got it to work finally.

Here's a schematic:

http://www.freephoto-i.net/users/new...sstaillght.jpg

It matches what longhornmail is telling you, and its right because it matches my truck minus the side marker lights which my truck isn't wired for.

Good luck.


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'69 3/4 ton C20 2wd w/ 350ci/400THM and a wood bed!
'69 3/4 ton Custom 20 2wd w/ ORIGINAL 350ci/4sp Manual and a wood bed (parts beast).
Seattle, WA.

*See pics of my trucks and project at www.webshots.com!

Longhornmail, i've got the worst headache after that post (ha ha). I don't have a clue on this wiring stuff. i guess i will keep looking. If you guys think of anything else let me know, i appreciate all your help.

Honestly, I think it is in the column. That is the most likely place for it since the wires an the chassis are all good.

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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
Need to pick up the one ton Longhorn with a PONTIAC 350/350soon.
Thanks every one!:)
Check out The Longhorn Webite.
If you need a pic posted, E-mail me at longhornmail@yahoo.com
Andy, in Columbus Ohio

I need to install a ground from the bed to frame, what location should i install this at.

You can probably find a bolt or nut on the taillight housing. Run a wire with ring terminals on both ends. Drill a hole in your frame and attach it. Be sure to scrape the paint and use star washers to ensure good contact over time.

well, since I'm cheap, and the same thing happened to me on the stepside recently, I just ran a wire from the bottom bed bolt on the outside, to a bolt on the frame, now my tailights/brake lights/turn signals all work correctly, so try a ground from under the bed somewhere, to the frame, and see if that helps. It sounds exactly like what I was dealing with. Here are a few shots of my "temporary" light fix:
[img]http://communities.msn.com/_Secure/0OwCFGmoSBh6o*Q5ALVOQJ7Vw7ZNIeu!MW*pnTQ3poDR2KTEXD*JszVhcX6csy9CzgOZzKDpiF2wVheSnUYkHKuOuCLa0Q62J/Picture-427.jpg[/img]
[img]http://communities.msn.com/_Secure/0NwBOBpIRytWo*Q5ALVOQJ9Q*DqKlEkFsEjSPt8iEfUzLrvXX2t7mBNA!vgkTmdBXcNDWHuSaUXv2JBAvxK6cyA/Picture-428.jpg[/img]

Sorry for being so long winded....

68