No reverse lights

[bfloyd]

My car has never had working reverse lights since I've had it. I'm in the process of installing a new stereo system with a reverse camera that feeds to the video screen of the head unit. I've always thought that the archaic light boards were the culprit , but that looks as if that's not the case. I've got the tail lights out to replace the circuit boards with the new DMCH boards, and tonight I was trying to wire in the camera to the reverse lights, and make a splice at the circuit board connector. I got the car started and shifted into reverse and took my tester to probe the connection. I got power on everything but the reverse connection.

I did replace my shift computer back in September , but didn't do any adjustments to the multi switch in the transmission itself.

Any clues?

[Michael]

I would imagine there is a dedicated switch for the reverse lights which is independant of the shift computer. It would have to be tied to the linkage itself, probably a microswitch or a gate switch on the selector or a switch on the trans housing on the other end of the shift linkage.

I would start there. I don't have my manuals handy or I would find it for you.

[DMCMW Dave]

The reverse light switch on an automatic is part of the passenger side electrical connector on the transmission. I've never seen one fail, so don't start with that.

More likely a wiring issue between the switch and the bulkhead connector (the red one). You will need a wiring diagram or at lead bulkhead pin diagram to chase it down. Or two bad boards/connections but I'm guessing you've already eliminated that, i.e. you can power the board and make the light go on.

[Rich]

Further to Dave's suggestion here's where to find the pinout diagram for the bulkhead connectors.

Post #19 in this thread: http://dmctalk.org/showthread.php?40-All-Wiring-Schematics/

These are the large harness plugs found on right wall of engine compartment back by the ignition coil.

The reverse light circuit goes thru the red one.

While you are there pull each of the bulk. conn.'s off, clean the contacts with something non-conductive. If one connection was poor others may be not far behind.


The reverse light switch on an automatic is part of the passenger side electrical connector on the transmission. I've never seen one fail, so don't start with that.

More likely a wiring issue between the switch and the bulkhead connector (the red one). You will need a wiring diagram or at lead bulkhead pin diagram to chase it down. Or two bad boards/connections but I'm guessing you've already eliminated that, i.e. you can power the board and make the light go on.

[16949]

The reverse light switch on an automatic is part of the passenger side electrical connector on the transmission. I've never seen one fail, so don't start with that.

Thank you, that is good to know. My reverse lights haven't worked in months. It's helpful to know what to disregard on first review.

[Ron]

+1 on all above.

You can eliminate adjustments easily since Reverse is between Park and Neutral..Have someone watch the lights as it is shifted between P and N slowly. If they flash (and you can hold them in some mid position to make them light up, suspect shifter adjustment, or as mentioned very rarely, multifunction switch.
Or divide and conquer:

Bypass the multifunction switch by shorting the LightGreen/White and Green/Brown wires together at the "L" shaped connector (Rev lights should burn, w/key ON).
12v (+) on the Green/Brown wire here should make them burn.
Similar for same colored wires at previously mentioned Red Bulkhead connector...
Check for power through fuse #16.

[David T]

+1 on all above.

You can eliminate adjustments easily since Reverse is between Park and Neutral..Have someone watch the lights as it is shifted between P and N slowly. If they flash (and you can hold them in some mid position to make them light up, suspect shifter adjustment, or as mentioned very rarely, multifunction switch.
Or divide and conquer:

Bypass the multifunction switch by shorting the LightGreen/White and Green/Brown wires together at the "L" shaped connector (Rev lights should burn, w/key ON).
12v (+) on the Green/Brown wire here should make them burn.
Similar for same colored wires at previously mentioned Red Bulkhead connector...
Check for power through fuse #16.

Get out Service Bulletin ST-16-10/81. There is a check to make sure certain plugs are connected (or not). The reverse circuit is different between the automatic and the 5-speed but the harness is the same for both, just used differently. If hooked up incorrectly that could be the problem.

[Ron]

Get out Service Bulletin ST-16-10/81. There is a check to make sure certain plugs are connected (or not). The reverse circuit is different between the automatic and the 5-speed but the harness is the same for both, just used differently. If hooked up incorrectly that could be the problem.If I'm following you...there are two red plugs in the box for the Bulkhead Connector (on some anyway) and there is a discrepancy in wire colors (see below).
39355

FWIW, my 81 June auto is like the red and schematic above...

[DMCMW Dave]

If I'm following you...there are two red plugs in the box for the Bulkhead Connector (on some anyway) and there is a discrepancy in wire colors (see below).
39355

FWIW, my 81 June auto is like the red and schematic above...

Often true, and if the wrong one is plugged in, you not only won't have backup lights, the car will start with the shifter in any gear.