No parking lights on the rear? 1977 K-20

[boostdtalon]

Ok so I got pulled over the other week for having no parking lights in the rear. brake, turn signals, and hazards work. Here is the kicker the license plate lights work as well. I thought it might be something with the rear harness as the other items worked. So the start my process of elimination, I checked for voltage at the rear harness plug and also at the lights themselves. I had power at the rear plug coming from the front. No voltage at the small bulbs or the main bulbs. I sure enough had power at the license plate wiring. I cleaned the rear harness plug and added some dielectric grease. I replaced my parking light and reverse lights for good measure. Did a function test with no new results.

I then pulled the rear harness out thinking that the 6 (one in five out) way splice had a failure somewhere. From my drawings this is the brown wire. Pulled the shielding away and the splice looks intact and no signs of corrosion. After doing a resistance check that showed nothing more than .3 ohms at any point. I'm somewhat stumped at this. I would think a grounding issue but that should cause the other lights to malfunction as well. That checked out fine as well.

I ordered a new rear harness from brothers trucks but it is on back order for at least another week or so and I need to get this fixed as the truck is my daily. any suggestions before I cut all of the wiring out and redo it? That's basically where I'm at now.

 

[Kain]

could be the switch thats bad...

 

[frankin5]

If you have power at the splice, it would be from there out. Does it have the right bulbs in it. check for power at the rear sockets to narrow it down. If no power there it is the wire from splice to socket. you could run a jumper from the splice to each socket to very power to the bulb.

 

[boostdtalon]

If you have power at the splice, it would be from there out. Does it have the right bulbs in it. check for power at the rear sockets to narrow it down. If no power there it is the wire from splice to socket. you could run a jumper from the splice to each socket to very power to the bulb.

Pretty sure something is wrong with the splice. That's the only conclusion I can come too. I'm gonna get some new wire tomorrow and rebuild it.

 

[boostdtalon]

Well looks like my grounds aren't working. Pulled the ground off of my LED and touched it to the chassis and the parking lights lit up. Ran out of time tonight, so tomorrow i'm going to build a ground wire for each tail light and see if that does the trick.

Thankfully my new harness and tail lights should be here by next week.

 

[boostdtalon]

Yep ground wires suck. Ran a new ground from the tail to the chassis and I now have functioning lights.

 

[Kain]

cool beans

 

[diesel4me]

I've never really understood how a rusty steel frame is supposed to carry the same amount of current as the positive side of an electrical system,which needs good corrosion free copper wiring and connections and heavy gauge cables to operate such things like starters and let the altenator charge the battery,etc..

Doesn't make sense to me to have the best low resistance conductors on the positive side,then rely on a corroded old high resistance steel frame to carry the rest of the load........but it works..

I suppose it would double the cost to have a separate ground wire for every item rather than just "grounding" things anywhere on the frame--but I wonder just how many less electrical troubles we'd have if they didn't rely on the vehicle itself to be the "ground".....