no backup lights

[Canadian Cuda]

well i've sorted out all electrical problems except my backup lights. i can't get them to work. they are brand new bulbs. there is no ground problem as i ran an extra ground from the taillight housing to the body, and i just installed a new neutral saftey switch. does anyone have an idea? all the rest of the rear harness works fine

thanks!

[dodj]

First of all make sure fuse # 8 is good. (it has to be said...we all forget to check once in a while  ). If the fuse is good then 12v power should be at one of the outside pins of your new switch. Unplug the switch and read with a dc meter, one probe to body ground and the other to one of the outer connections on the plug. If you read nothing, try the other outer connection (on the plug not the switch). If neither one reads 12vdc then you have a wiring harness problem-most likely between the bulkhead connector and the switch. If you do have 12vdc, move on to the driver's side kick panel. Remove it. In there you will find an eight wire rear body lighting connector. Pull it apart. Connection #6 is a white wire with a tracer on it. With your meter measure from that wire to body ground. You should read 12vdc. If you don't, the the problem is between the bulkhead connector and the rear body connector. If you do have 12v then reconnect the connector and remove the back-up light from the housing. Remove the bulb and measure with your meter from the single contact in the light socket to body ground. If you have 12v then your bulb is bad or the ground is bad. If you don't have 12v then the wiring between the rear body connector and the light socket is bad.

[hooD]

First of all make sure fuse # 8 is good. (it has to be said...we all forget to check once in a while  ). If the fuse is good then 12v power should be at one of the outside pins of your new switch. Unplug the switch and read with a dc meter, one probe to body ground and the other to one of the outer connections on the plug. If you read nothing, try the other outer connection (on the plug not the switch). If neither one reads 12vdc then you have a wiring harness problem-most likely between the bulkhead connector and the switch. If you do have 12vdc, move on to the driver's side kick panel. Remove it. In there you will find an eight wire rear body lighting connector. Pull it apart. Connection #6 is a white wire with a tracer on it. With your meter measure from that wire to body ground. You should read 12vdc. If you don't, the the problem is between the bulkhead connector and the rear body connector. If you do have 12v then reconnect the connector and remove the back-up light from the housing. Remove the bulb and measure with your meter from the single contact in the light socket to body ground. If you have 12v then your bulb is bad or the ground is bad. If you don't have 12v then the wiring between the rear body connector and the light socket is bad.

Man!  I'm going to ask you my electrical questions when and if I have any in the future.

[BruteForce]

Those old mopar electrics are pretty simple (don't let that rat's nest of a wiring diagram fool you). Think of electricity like water flowing through a pipe, and you're good to go for about every electrical problem in the car. The water pressure corresponds to voltage, and water flow corresponds to amperage. The battery is the source of the water pressure, it's like the tank up on stilts in a small town. The water wants to flow from the tank to the ground.

If your lights aren't working, it's because there's either a break in the water pipe going to the bulb, or a break in the pipe going from the bulb to the ground. With a voltmeter, you can see the pressure in the wires.

Pick yourself up a cheap multimeter from Radio Shack, and you'll be good to go for debugging it. Sometimes it's easier to use a test lamp to check for voltage, or even a buzzer, if you'll be tracing wires while upside down under the dash!

[Canadian Cuda]

thanks for the help guys i'll check today. dodj that has to be the most thourough answer i've gotten on this site( and there's been alot). i've learned alot about wiring throughout the entire and this is the last roadblock. bruteforce i do have a multimeter and test lamps so i think i'll find the problem

you guys rock

[Canadian Cuda]

so here's where i'm at. have power at the plug but not at the connector to the rear harness. so th problem is between the bulkhead connector and the rear harness? what do i do next? check for damage or disconnection of the white wire?
thanks

[Chryco Psycho]

yes you have power to the reverse swithch & back into the cra through the bulkhead then there has to be a problem either at the plug to taillights or betweent the bulkhed & the plug by the kick panel

[Canadian Cuda]

problem solved thanks to you guys and the wiring diagrams I found the problem. it was in the engine compartment. the two black wires which i guess are from the tranny had been replaced and pieced together in multiple joints and one of the wires was broken off in the plug so rewired the plug with the correct wires an plugged it in, and sure enough... lights!

Thanks everyone!

[BruteForce]

You're right that the two black wires go to the reverse switch on your tranny. Splices often go bad if they're not crimped and soldered.

[dodj]

Glad to hear you found the problem. I had a similar problem a few years ago when those wires got burned by my exhaust. Make sure you secure them away from the exhaust but with a little slack so when you launch hard the wires don't tighten up. 

[dodj]

Those old mopar electrics are pretty simple (don't let that rat's nest of a wiring diagram fool you). Think of electricity like water flowing through a pipe, and you're good to go for about every electrical problem in the car. The water pressure corresponds to voltage, and water flow corresponds to amperage. The battery is the source of the water pressure, it's like the tank up on stilts in a small town. The water wants to flow from the tank to the ground.

If your lights aren't working, it's because there's either a break in the water pipe going to the bulb, or a break in the pipe going from the bulb to the ground. With a voltmeter, you can see the pressure in the wires.

Pick yourself up a cheap multimeter from Radio Shack, and you'll be good to go for debugging it. Sometimes it's easier to use a test lamp to check for voltage, or even a buzzer, if you'll be tracing wires while upside down under the dash!

Hey BruteForce.. Are you an electrician too?

[BruteForce]

Are you an electrician too?

No, I'm a mechanical engineer. But I paid my way through college doing electronic technician work. I played a bunch with electronics as a kid, and built some computer equipment from scratch.

The electrical system on those old mopars is very low tech in that all you need to debug them is a multimeter. For me it's the easy part of the car, it's the body work you guys do that I'm in awe of 

[Chryco Psycho]

 
 the wiring is simple

[shadango]

First of all make sure fuse # 8 is good. (it has to be said...we all forget to check once in a while  ). If the fuse is good then 12v power should be at one of the outside pins of your new switch. Unplug the switch and read with a dc meter, one probe to body ground and the other to one of the outer connections on the plug. If you read nothing, try the other outer connection (on the plug not the switch). If neither one reads 12vdc then you have a wiring harness problem-most likely between the bulkhead connector and the switch. If you do have 12vdc, move on to the driver's side kick panel. Remove it. In there you will find an eight wire rear body lighting connector. Pull it apart. Connection #6 is a white wire with a tracer on it. With your meter measure from that wire to body ground. You should read 12vdc. If you don't, the the problem is between the bulkhead connector and the rear body connector. If you do have 12v then reconnect the connector and remove the back-up light from the housing. Remove the bulb and measure with your meter from the single contact in the light socket to body ground. If you have 12v then your bulb is bad or the ground is bad. If you don't have 12v then the wiring between the rear body connector and the light socket is bad.

Does that pin in that plug get power only when the ignition is in the "run" position?

If so, what is an easy way to test for power there if someone is by themselves.....

I have heard you can burn up your ballast/ignition module/coil by leaving the ignition "ON" without the car running......   

[Chryco Psycho]

yes it is a key on only circuit
test light at the firewall is how I would check it you can also use a test light at the tranny plug , it is not going to hurt anything to have the key on for 5-10 minutes even