Rear tail lights... Only some work but not always?

[K10mashup350]

So I just replaced me taillight harness from fuse panel all the way back to the lights (including the "t" for the actual lights) so "technically" 2 harnesses. The reason was when I bought this truck they had every wire harness cut an hacked an almost nothing worked an the taillight harnesses weren't even there....
But my issue is that they don't work running lights work always, and sometimes(not often at all) the break and hazard (not signal) will work drivers side only and nothing on pass side. Fuses look good an flasher seems to work as the front works....

More about the harnesses I put in:
They were not new or 100% intact, I did have to "reconnect" a few locations/light sockets and I did so with heat shrink then fully wrapped the harnesses with wire loom and electrical tape to ensure no wires can come in contact with anything an "rub" to where there could be a short in the lines...
As I had all the wires "bare" I inspected them for cracks/imperfections and corrected the few that I did find, so in all aspect the harnesses are now "new" without defects.... But I still don't have working taillights....

The attached pic shows the lights that do work constantly everything else either don't work, or is a swing n a miss to if it will work.

Any help on this would be greatly apperitiated so that I can drive my truck, an be able to get my certification...

Thanks

[Axle]

Start with your Ground. Black wire screwed to the bed sheet metal behind the driversside taillight.

Since you mention it is not a new harness, there is a good possibility your ground wire is corroded, and may even have broken during reinstallation.
Run a dedicated ground wire from the front of the truck to the back and connect it with an aligator clip to your harness ground and test your lights. If all works, service the ground wire, and if desired, run a dedicated wire from the battery (or other good ground at the front of the truck) to the rear.

Alex.

[BADAZ chevy guy]

I agree. Also, make sure your body has a ground strap from the battery.

[K10mashup350]

So for an update I've grounded everything and still havering the same issue, all wires are good no cracks nothing .... Only thing I haven't done is run a ground from battery to the taillight sheet metal ground to check it that way

[willett]

Next time one of your lights cuts out pull it and stick a volt meter between the hot side and a COMPITENT ground. If your getting a full 13.whatever then you have more sanding to do. Make sure your box itself had good ground to the chasssis and the chassis is good to the engine/battery as well.

Don't forget, dielectric grease is your friend and just because your test light illuminates it doesn't mean your getting full power to that point

[K10mashup350]

I haven't had them work since I started this thread.... Only have my running lights... I'll run a temp ground from battery to the "sheet metal" ground to see if I can get them to work.... It really sucks cuz I want to drive my truck but can't till I get this figured out, not having break light or signal lights it won't pass inspection

[K10mashup350]

So I still have no clue as to what the hell is going on with this... Tried a new plug(just incase) grounded everything I could thing of to the frame/battery, I even ran temp ground from battery to "sheet metal" ground behind light an still nothing? If I put my volt meter to the "T" plug I can get a reading, but it's very low... Nowhere near 13v..... Any more ideas?

[willett]

No power = no continuity



Asuming you tried grounding everything properly it sounds like you have a poor connection or a bad wire on the hot side of the circuit. Dig up a wiring diagram on here and find out which colour the tail light wires are. Start at the fuse block and check power at your fuses. If that's good check power on the wires where they come out at the back of the fuse block. A few feet past that if memory serves me right there are some weatherproof connectors that may not be weatherproof anymore.

Get a wiring diagram and fire up that multi meter. I notice your out Ontario way, I hear they're not afraid to use road salt out there

[K10mashup350]

I no longer have any "connectors" it's full straight wire from back of the fuse panel to the "t" to split off for taillights, I can get a good reading out of one of the terminals (not sure what side as it's at the plug) of about 12v "jumping" with 4 ways but the other is real low... An again even with a temp ground from battery I have no break/turn/4ways... I have checked all fuses there good and flasher works the front on 4way or turn... Only thing I have at the rear is running lights

I also have a Hanse manual with all diagrams... I reworked every harness in the truck an this is the only one that don't work

[K10mashup350]

So I've managed to figure ou one side since my last post, I have driver side back 100% brake and turn/4way, but still only running lights on pass side...

[willett]

Make sure your bulb has both filaments in tact

[K10mashup350]

First thing I did was replace both bulbs... Both brand new fresh outta the pack...

[willett]

Is there power coming out of both sides of the tee? This is not difficult problem solving