no rear lights

[78C10 sleeper]

None of the rear lights on my 78 C10 are working. And I have checked the fuses,flasher,head light switch and brake light switch and I replaced the turn signal light switch.the truck used to be a 6 cylinder and some of the wiring is hacked and it has extra wiring electric fuel pumps nitrous electric fans ect any help would be very much appreciated thanks

[rich weyand]

The first thing to think any time there is an electrical problem on a vehicle is "I wonder if there is a ground problem."  Two reasons: 1) we almost always think in terms of the hot lead (fuse, switch, etc.), ignoring the ground, and 2) it usually is the ground.

The two critical grounds on the 78 C10 are 1) the ground strap from the firewall to the rear of the passenger-side head on the engine and 2) the ground from the front of the driver-side head of the engine to the frame rail.  These are copper braids with an eye on each end.

If those aren't there, just about anything can happen electrical in the truck, like headlights flashing with the turn signals and such.  And these straps are often left off when people do work on these trucks.

So check those first.

[78C10 sleeper]

I did check the ground on the back of the head but it does not have one on the front of the head also it has a ground that goes from the tail light bucket to the bed but on the passenger side there is none is that correct that for the reply

[rich weyand]

There has to be a ground strap from the power steering bracket upper bolt to the top side of the frame rail about even with the back of the steering box.  Right now both your cab and engine have intermittent ground, or things are finding ground paths in weird ways.

With regard to the rear lights, there should be a sheet metal ground on both sides.  See: http://www.73-87chevytrucks.com/techinfo/wiring_diagrams/77-80_chass_rr_light.jpg

[78C10 sleeper]

Its manual steering. Im going to buy a strap today where should I place the strap on the motor would the head or an avalible hole in the block be ok

[Boone83K10]

Did you check the bulbs...

[Irish_Alley]

there doesnt have to be a ground from the pump to the frame. there is usually one on the alt bracket to bat/frame. but have you done anything lately to the truck?

[78C10 sleeper]

Yes the bulbs are new and I did put a new cable from the alt to the bat when I installed the motor about 4 years ago.and yes I've done a few things to it put a turn signal switch and some new electric fuel pumps

[rich weyand]

Re: the engine ground strap: There's a screw on the top side of the frame rail about even with the rear of the steering box.  That's one end.  The other can go to the outside front valve cover bolt.

[Irish_Alley]

theres allot of screws on my truck allot of loose screws including the one behind the wheel lol. but not saying that one is not supposed to be there just saying that one is not necessary. although i never heard of a problem with having too many grounding straps. sorry about the last edit to my last post but the grammar was killing me and i wrote it lol

[rich weyand]

He's also missing the sheet-metal ground on one side, and that  won't help either.

[78C10 sleeper]

Its been raining all day haven't ben able to work on it and also one head light has always ben brighter then the other could that be a ground issue to thanks for the help

[rich weyand]

Yeah, there should be a ground from the headlights harness on both sides as well, as shown in this diagram.  One is listed as frame ground, the other as sheet metal ground.
http://www.73-87chevytrucks.com/techinfo/wiring_diagrams/77-80_250_I6_eng_frt_light.jpg

[78C10 sleeper]

Ok so I redone the missing bed ground and now the lights work when the head lights are on but not when there off and the signal lights wont blink

[Irish_Alley]

Signal won't work with the headlights off. Might be flasher swap flashers and see what happens