Reverse Lights Not Working-Trouble-shooting/Narrowed Down Problem But Now Stuck. Help

[DeloreanJoshQ]

Back in May my reverse lights worked after putting the car back together and beginning to drive it for the summer. The original back-up light switch was bad so I replaced it with a new one during the process.

After this weekend it was noticed the backup lights no longer work; I don't know how long this has been going on.

To trouble-shoot the problem and narrow down suspects I did the following:

-checked the "power wire" going to the backup light switch with a test light and the wire has power with the key on in the ignition.
-hooked the "power wire" to one side of the switch and tested the other connector on the switch with the transmission in and out of reverse. The test light indicates power traveling through the switch with the transmission in reverse so this should prove the switch works....
-Removed one of the rear taillight assemblies. Disconnected the wiring harness from the circuit board and tested with a test light. There is no power going to the backup light wire connection with the transmission in reverse. I also tested the other end of the wiring harness for the turn signals and the test light blinked with the hazards on so I know I was checking the wiring correctly. This should eliminate the backup light bulbs and circuit boards...for now...
-I messed with the black bulkhead connector that connects to the rear bumper lighting to see if there was a loose connection; still no reverse lights.

So now I have the problem narrowed down to between the backup light switch and connector that that hooks up to the tail light circuit board.

What else can I do besides unravel all of the wiring to try to trace the break back to the switch?

Thanks,

Josh Q

[DMCMW Dave]

Did you connect the two wires together at the transmission?

[DeloreanJoshQ]

Did you connect the two wires together at the transmission?

I did and no reverse lights....this would remove the backup light switch from the equation.....

[Bitsyncmaster]

There is a connector in the engine harness on the fire wall (two pins). I've seen that connector cause backup light problems. The pins get wet and oxidize.

[DeloreanJoshQ]

There is a connector in the engine harness on the fire wall (two pins). I've seen that connector cause backup light problems. The pins get wet and oxidize.

I found the connector Dave. It was connected, so I disconnected it and reconnected it. When I did that I heard a buzzing sound like the fuel pump re-initiated. I pushed the connector together, looked at the back bumper, and Eureka! the reverse lights now work! So the 2-pin connector to the reverse lights also powers other things in engine bay?

Thanks again to both Daves!

[Bitsyncmaster]

I found the connector Dave. It was connected, so I disconnected it and reconnected it. When I did that I heard a buzzing sound like the fuel pump re-initiated. I pushed the connector together, looked at the back bumper, and Eureka! the reverse lights now work! So the 2-pin connector to the reverse lights also powers other things in engine bay?

Thanks again to both Daves!

It's just for the reverse lights. It must have caused an electrical noise that made the RPM relay prime when the reverse lights came on.

[DeLorean03]

I found the connector Dave. It was connected, so I disconnected it and reconnected it. When I did that I heard a buzzing sound like the fuel pump re-initiated. I pushed the connector together, looked at the back bumper, and Eureka! the reverse lights now work! So the 2-pin connector to the reverse lights also powers other things in engine bay?

Thanks again to both Daves!

This should go in the "Problem/Solution Found" portion of the resources.

[sean]

Done.

[DMCMW Dave]

It's just for the reverse lights. It must have caused an electrical noise that made the RPM relay prime when the reverse lights came on.

We've seen thing like that - you make a big pulse anywhere near the distributor and the pickup coil will pick it up, fire a pulse, and the RPM relay will come on for a few seconds.

Be careful running wires in that area or you can get misfires at really wierd times.

[Bitsyncmaster]

We've seen thing like that - you make a big pulse anywhere near the distributor and the pickup coil will pick it up, fire a pulse, and the RPM relay will come on for a few seconds.

Be careful running wires in that area or you can get misfires at really wierd times.

It's most likely another ground offset problem but I agree, you want that pickup coil wire routed clear of other wires.

Incandescent light bulbs cause a very heavy current flow when you first turn them on. The tungsten filament is almost a dead short when it is cold.

[pezzonovante88]

I found the connector Dave. It was connected, so I disconnected it and reconnected it. When I did that I heard a buzzing sound like the fuel pump re-initiated. I pushed the connector together, looked at the back bumper, and Eureka! the reverse lights now work! So the 2-pin connector to the reverse lights also powers other things in engine bay?

Thanks again to both Daves!

Where exactly is this connecter?

[DeloreanJoshQ]

Where exactly is this connecter?

I believe the connector is in the area of the wires zip tied to the rod at the back of the engine bay...just follow the plug from the reverse switch backwards....

[pezzonovante88]

The two wires connecting to my reverse light switch have come loose. How do I know which wire goes to which connector and is there any risk of damage if I just do trial and error?

[Bitsyncmaster]

The two wires connecting to my reverse light switch have come loose. How do I know which wire goes to which connector and is there any risk of damage if I just do trial and error?

Does not matter which wire goes to which terminal.

[Delorean Industries]

The two wires connecting to my reverse light switch have come loose. How do I know which wire goes to which connector and is there any risk of damage if I just do trial and error?

If they keep giving you trouble you can apply a little bit of tension to the connectors to squeeze the contacts closer together. Just don't RTV the boot on as you will have a mess when you need in there again.

[pezzonovante88]

Thank you gentlemen. All fixed.

[NightFlyer]

Can anyone provide a picture of this rubber boot that supposedly goes over the reverse light switch connectors/electrical lines? I can't find it mentioned anywhere in the parts manual. I also don't think my car has it, as this is what my switch looks like:

21945

[pezzonovante88]

It's kind of like this (from a Porsche):

http://www.autoatlanta.com/itemgraphics/B91461349100.jpg

It's just a little rubber boot that fits over top of the connectors and terminal.

[jawn101]

It's kind of like this (from a Porsche):

http://www.autoatlanta.com/itemgraphics/B91461349100.jpg

It's just a little rubber boot that fits over top of the connectors and terminal.

Really?? I've never seen one on a D. Makes sense given the exposed nature of that switch....

Would love to get one but I also don't see them on Houston's site anywhere.

[painterdave72]

they are part of the reverse harness.. if you buy a new harness it will be on there.