Brake Light/Turn Signal wiring

[jrclark32]

I recently acquired a 78 C10, and none of the lights on the rear of the truck were working. I thought it might be a ground issue, so I cleaned all those up, and when that didn’t help I traced the harness, and found that all 4 wires going to the back were cut and tied off underneath for some reason.

I used a jumper from the battery to the cut wires, and all the lights work, so now I’m just trying to figure out where to terminate them. I found the reverse light wire, and spliced into a wire for the tail/running lights.

I can’t find any wires coming through for the turn signals/brake lights. Where should those be running from?

Thanks for your help!

 

[C10MixMaster]

I recently acquired a 78 C10, and none of the lights on the rear of the truck were working. I thought it might be a ground issue, so I cleaned all those up, and when that didn’t help I traced the harness, and found that all 4 wires going to the back were cut and tied off underneath for some reason.

I used a jumper from the battery to the cut wires, and all the lights work, so now I’m just trying to figure out where to terminate them. I found the reverse light wire, and spliced into a wire for the tail/running lights.

I can’t find any wires coming through for the turn signals/brake lights. Where should those be running from?

Thanks for your help!

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[Charlie]

 

[MrMarty51]

YUP, welcome to the GMSB JR.

 

[jrclark32]

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Thanks!

It looks like my wires are missing from the connector entirely. Is there a way to tap back into this?

 

[dvdswan]

Verify you have the wires on the inside as well. If the PO(s) were stupid enough to ripped out the rear lights wiring... who knows.

IMO, go purchase a trailer wiring harness, about $20 at local parts store I think (cheaper than buying each individual wire), you should be able to purchase the connectors for the block on the firewall, the bolt in the center of the block, unscrew and verify the old connectors are not still in there. Run the cable, install the connectors and be sure to build a harness for lights in the back.

The fourth wire can be used as the back up lights.

If you do buy the individual wires be sure to get the correct colors for each.

 

[jrclark32]

Thanks for all the help so far guys!

I’ve been probing the firewall connector, and I’ve found the spots where I need to tap into this block.

What kind of connector do I need?

 

[C10MixMaster]

Thanks for all the help so far guys!

I’ve been probing the firewall connector, and I’ve found the spots where I need to tap into this block.

What kind of connector do I need?

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they are GM 56 or Packard 56 connectors. I get mine off of Ebay. buy them in bulk they fit almost everything on these old trucks

 

[jrclark32]

Okay... cool. I ordered some of those connectors, but I was able to modify a spade to work temporarily.

I’m happy to report that she passed the state safety inspection, and is running, driving, and legally back on the road for the first time in over 13 years.

I’m sure I’ll have a million more questions as I gradually sort through all the little issues a 41 year old truck has. Thanks for your help!