91' No lights or power to rear of truck

[Aaron285]

I have no tail lights, blinkers, or backup lights. Head lights and everything works up front except blinkers. Where should I start testing for voltage?

 

[Uncle Gump]

The rear taillamp harness connector.

 

[ericbphoto]

The rear taillamp harness connector.

And the ground connection on the rear crossmember.

 

[Aaron285]

So. Disconnect the harness, turn on lights and test DC, ground to each pin?

 

[franklin2]

So. Disconnect the harness, turn on lights and test DC, ground to each pin?

Big mistake people make when testing lighting circuits is to unplug the wiring. Try to back probe the connectors leaving everything connected. If you have a poor connection somewhere, it will support the current draw of the meter and give you a false reading. But the poor connection will not support the current draw of all the lights, so then the voltage drops. You want to put the meter in the circuit with the bulb load present. Another alternative to that is to use a testlight. The light in the testlight will draw enough current that the poor connection will not support it and won't make it burn bright.

The most common spot for wiring problems in the rear is a previous owners trailer plug wiring. They usually do not have very good wiring practices and it's pretty wet and dirty back there. Check for any trailer wiring first.

 

[Aaron285]

And the ground connection on the rear crossmember.

Where is that ground exactly located? can you post a picture. Thanks

 

[Eddo Rogue]

check the fuses.

 

[Aaron285]

I checked them. All good. I have 12v at the pedal switch to ground. I jumped to the back of the truck after that quick test and didn't see a ground wire. Where is it located? I have to check voltage and the plug from frame rail to harness to tail lights. I will test with the harness/ plug attached. Should I test pin to pin or pin to ground, and what color wire(s) and voltage and I'm looking for when pedal is pressed, lights on, etc.

 

[dvdswan]

Follow the wire looms from each light to the connector, you should have a ground wire come out of the loom to the frame or body crossmember. If it goes to the bed crossmember then check the bed for another ground connection to the frame.

Don't forget the license plate lights also. Do you have a trailer harness on the truck also?