Reverse lights not working, what could be the cause?
 

1976 912E, cleaning up a wiring disaster created by someone prior to my ownership. A friend is helping me with this effort, as the refurbished tail light assembly on the drivers side was being installed, a quick test identified that the reverse light was not working. All other lights in thie drivers side assembly function properly.

It appears, when the passenger side was tested that everything was fine except the reverse light/socket was not giving a reading.

What could be the reason/s?

Thanks for your insight.

Mike

Mike - you need to use a wiring diagram to test and see where the problem is. You have the 915 transmission, so the reverse switch is at the very front of the transmission. You can just see it between the chassis and the transmission mount crosspiece. It should have two wires plugged into it. These wires have bullet ends, not the more common spade lugs. I can't recall if this plug grounds the backup lights, or supplies the voltage, but you can easily tell that from the diagram.

Our host has several wiring diagrams on this website. None for a 912, but that doesn't matter - use the one for mid-year (2.7-3.2, doesn't matter) 911s. For that matter, I suspect that other than the fuse box, the diagram for the early 911s will do also.

the reverse switch should be covered with a rubber hat. carefully pull the leads out and touch them together and the reverse lights should illuminate with the ignition in the on position (engine off).

Walt and schumicat, thanks for your input. I will look into the reverse switch and see what happens.
Regards,
Mike

if you find it wet, you may want to replace it on your next gear lube change.

If you have to dig deeper, check for an open circuit and then start thinking about a broken conductor. I just fixed my reverse lights when I found a broken conductor. I guess 30 year old wires just get tired sometimes, or the PO let the wire get slapped around by the CV studs.

Bill

Bill's advice reminds me that the wiring for this switch runs back along the transmission up past the starter and through the engine surround tin, where it joins the main engine wiring loom. It travels in that loop to the big 14 pin connector which attaches most of the engine wiring to the rest of the car. With the circuit diagram in hand, you can probably dope out which wires in that connector are for the reverse light circuit, and use that to help troubleshoot.

Thanks again fellows for the input. I didn't get a chance to address this yesterday, but at least have a better direction to go in when I do.
Regards,
Mike