Reverse light troubleshooting Options

[Red72]

OK, so I picked up a '72 1.7 through the winter, and I'm working on getting items cleared before I go for safety to get it on the road. While underneath, I found that a terminal from the backup light switch on the transmission was broken...remove the switch, it's not even the right item, and the pin through the trans housing isn't there either. OK, so I replace all of that, still no reverse lights...take the lenses off, no bulbs...and it appears that a PO has re-sprayed the interior of the light, painting some of the conductive bits in the process. (IMG:style_emoticons/default/wacko.gif) Now I'm trying to figure out how the PO had it safetied in the first place...I suspect it was simply signed off without checking anything.

So I'm going back to basics to trace the whole system, and make sure things are good electrically all the way through, before I tackle trying to clean any excess paint away. I've found the lines at the regulator board which go to the switch, but there is no DC voltage across them when the car is on...there is a slight AC voltage...but I'm assuming I should be getting DC right from the get go. Turn signals work just fine, so I know the fuse for that grouping of lights is good.

What kind of voltage should I be seeing go to the backup light switch? Thoughts regarding anything on the regulator board that might affect not getting voltage to the switch?

Thanks for any help...planning to start a thread soon to document the work I'm going to be doing overall. The body is pretty sound, the interior needs some work, but a whole lot less work than the scratch build Lotus 7 project I parted out to get something like the 914 that I could drive.

Stephen

[914Mels]

you should have battery voltage at the switch, nothing real special in this circuit.

[AvalonFal]

If you unplug the two wires to the switch, ignition on, & touch them together, back-up lights should turn on. If so, switch is the problem. If no lights, check for 12V at the wires. If no voltage, problem is before the switch. If you have juice at the switch, problem is after switch (wiring, bulbs, bulb socket contacts).

Paul

[Red72]

Yeah, I've confirmed there is definitely no power at the switch... Hopefully tomorrow I can start tracing the regulator board... I know there at least appears to be some empty points on the board...whether they are involved, I'm uncertain...it seems the turn signal and reverse lights are on the same fuse... So with the signals working, I know it's not that.

Stephen

[914Sixer]

There is a small pin behind the backup light switch in the transmission that is known to wear out. It completes the circuit to make the lights come on.

[GeorgeRud]

You might actually want to remove the regulator board and check the connections on the bottom. They can corrode and a clean up or some solder may certainly help. Most of the current paths are just running from the front harness location to the rear connector through a relay or fuse, so it's really a simple system.

Trying to figure out what previous owners have done can be an exercise in frustration!

[davesprinkle]

And when you solve all the other problems, you'll find that the switch contacts have high resistance. (I'm guessing that's because of the transmission oil.) So high that your bulbs won't light. My reverse lights turn on only 1 out of 10 times. Frustrating.