No rear lights

[Matt S]

I'm in the process of getting my new to me M1031 on the road. I've found the wiki link and I've downloaded all of the tm's I can find.

I've started with the electrical system. Currently I now have working headlights (high and low beam) with the LMC style relay. I've replaced the headlight/dimmer switch in the cab. I have working turn signals in the dash and out front. I have cleaned and/or replaced all the bulbs in the instrument cluster and confirmed they work thru the gauge cluster connection. With the dash plugged in, I get all the lights to come on except 4WD. I have confirmed all the fuses are good by doing a continuity test.

My current issue is with the lights past the cab. I have no rear lights. No brake lights, clearance/marker lights, reverse lights, or rear turn signals. I've tested the service light switch and it appears to be working. I've traced the wiring from cab rearward and I can't find anywhere that it's disconnected.

Any ideas of what to look at next?

 

[DREDnot]

Are your blackout light switches installed? Removed? Bypassed?

Mine were missing from a PO and was the source of my taillight woes. The connector/bypass was missing one jumper wire.

 

[Matt S]

I have a switch on the dash for the lights but I don't have a rear bumper if there were any there. Where do I need to look?

 

[DREDnot]

There were some switches in there that controlled the backout drive features. The switches need to be present and working, or bypassed with a few jumper wires

in order for lights to work on the truck

 

[cucvrus]

View attachment 709530

There were some switches in there that controlled the backout drive features. The switches need to be present and working, or bypassed with a few jumper wires
View attachment 709531
in order for lights to work on the truck

DREDnot. Do you have your switches? Happy Holidays.

 

[MarcusOReallyus]

I have a switch on the dash for the lights but I don't have a rear bumper if there were any there. Where do I need to look?

The blackout lights were in the rear bumper, so if you don't have the bumper, it's almost certain that somebody messed with the BO light system. That's probably the source of your problem. That's why cucvrus asked about the switches - if you don't have them, we know that system's been messed with, which is a good clue about where to look for your problem.

 

[Matt S]

The blackout lights were in the rear bumper, so if you don't have the bumper, it's almost certain that somebody messed with the BO light system. That's probably the source of your problem. That's why cucvrus asked about the switches - if you don't have them, we know that system's been messed with, which is a good clue about where to look for your problem.

I don't have a rear bumper but I do have all of the switches in the dash. On the service light switch, the on and blackout modes seem to work. Are you talking about the switch on the far left? If I don't have a rear bumper, should I bypass the left switch with jumpers until I can get a bumper?

 

[Evil Dr. Porkchop]

should I bypass the left switch with jumpers until I can get a bumper?

Don't worry about it, unless they modified some wiring you don't need the blackout lights or rear bumper to have working taillights. Make sure the taillight harness across the back is still hooked up and intact though. Since the bumper is gone it's not unlikely they messed with the wiring back there.

 

[Matt S]

Make sure the taillight harness across the back is still hooked up and intact though. Since the bumper is gone it's not unlikely they messed with the wiring back there.

Great suggestion. I found a bunch of cut wires back there. I'll look up the diagram and see what's going on.

 

[MarcusOReallyus]

There ya go.

If the switches are still in place, and you have working lights in the front, then your switches aren't (directly) the problem. Wire hacking is probably the the problem.

 

[DREDnot]

DREDnot. Do you have your switches?

No, Mine were gone when I got it

 

[cucvrus]

I know of
a guy in Pennsylvania that has stuff like that. You know that guy? Happy Holidays. Hey how about some support for my CUCVV as MV of the month. Please vote.

 

[Matt S]

Since the bumper is gone it's not unlikely they messed with the wiring back there.

This was the problem. Thanks for the advice. Every single wire was cut and tucked into the frame. I found and fixed two bad bulbs but now I have all the running lights, turn signals, brake lights, and reverse lights working!

Now to reinstall the dash and charge the batteries from all the testing.