Hey guys, I'm working on my buddy's 1969 350/4spd and I'm having an issue with the backup lights not working. I've checked the backup switch connector in the engine bay and have 12V on the PINK wire on the FIREWALL side and SWITCH side, and when in reverse I have 12V on the BOTH sides of the LT GREEN wire as well, so I know I have power to the switch and coming back out with the gearbox in reverse. I don't seem to be getting the 12V back to the lights. Bulbs are good, but I swapped them out for the hell of it with no luck. I checked the grounds and from what I can tell everything looks good. I used a power probe and tried putting ground into the housing with no change. Used my multi-meter and checked the backup light socket with the bulb out and car and reverse and I'm not getting any power.

I don't have a wiring diagram handy for his car, just for my 80 which is an auto and no help. What do you chrome bumper 4spd guys think? Where should I be looking for a break. I know that LT GREEN wire is what brings the power back. I followed it into the cabin and up to the center console. I'm pretty sure it's similar to my car in that it basically just goes from there straight back to the rear of the car.

I appreciate any input!

Also working on an inoperative horn, you can hear the relay clicking but no power to the horns, so I'm thinking the relays bad. Annnd his steering wheel is upside down but the turn signal cancel works. I have to look up Jim's steering papers to get a little more into that.

 

You said that you have 12v on the green wire when in reverse. That tells me that the switch is doing what it should. The green wire supplies the 12v back to the lights through a connector. I believe the rear harness connector is located on the drivers side under the dash and the harness supplies the rear end electrical loads. It runs along the drivers side up over the wheel well and through the bulkhead via a grommet. I guess your best bet is to look at the wire route and see if there are any obvious issues.

 

Yeah it must be a break somewhere in there. I'm going to order a wiring diagram for him so I can hunt it down. Thanks for the input! It also just occurred to me that I should probably check continuity in the Lt Green wire from where I can access it in the cabin to the back and then go from there.

Horns are both dead, they both had 12V running to them when the button was pressed, and when I pulled them and bench tested them neither worked, so I'll be ordering those.

Steering wheel was installed 90* out and then the alignment was out about 5* from there. Took apart the steering column down to the canceling cam, spun that and the hub and reinstalled it straight, then aligned it (I do all the work on the weekends at a shop I used to work at, so I have an alignment rack). So that all seems to be squared away.

Now I have a new problem that I need to research on here and may start a new thread for. While doing the alignment I found the passenger side outer tie rod end was hitting the inner tire sidewall. The contact has been significant enough that its worn a decent groove into the sidewall. I don't know what could be causing this aside from a bent knuckle, but I don't see any obvious signs of previous impact and those things don't bend easily. Not good though. I'll post some pictures when I get home. I'm going to advise him to not drive/drive cautiously (avoid highways) until we straighten it out and replace that tire. I don't like the risk of a blowout!

 

Something else to add to the backup light issue. The car keeps blowing the turn signal/backup light fuse. It's strange because if you replace the fuse the backup lights still don't work as described above, but the turn signals do. The weird thing is while the car is sitting you can run the turn signals and they work and you can put the car into reverse and get 12V on the Lt Green wire, and the fuse doesn't blow. But once you start driving it blows at some point.

Any ideas?

I'm going to try replacing the fuse again and then disconnecting the backup light connector in the engine compartment to try to eliminate that circuit so I can rule out the turn signal circuit as being the issue. I think it's probably a good sign that there's a break in that light green wire somewhere in the rear, but it's just weird it doesn't blow the fuse while sitting. Maybe it's only contacting a ground and shorting out when the cars moving?

 

Just wanted to update this in case someone else needs help in the future.

I traced the circuit and found the break. As I mentioned, I had 12V on the pink wire going to the switch, and 12V coming back out of the switch on the light green wire while in reverse. The light green wire goes directly back to the backup lights, but I wasn't getting 12V at the end of the wire by the bulb sockets, so I knew it was broken somewhere. In addition, although the backup lights never worked, the turn signal/back up light fuse kept blowing BUT, only while driving. You could replace the fuse and operate the turn signals while sitting there and they'd work fine, backup lights wouldn't work at all, and then when you drove around the block the fuse would blow and the turn signals would stop working.

I replaced the fuse and disconnected the backup lights at the engine bay connector just to rule out the turn signal circuit, even though it was pretty obvious the issue was in the backup circuit. With the backup lights unplugged and the fuse replaced I drove the car without the fuse blowing confirming the short was in the backup light circuit (again, obvious, but not confirmed). I went back to tracing the circuit, next checking the light green wire under the dash just after where it enters from the engine bay, 12V present there. Next I checked where the light green enters from the rear, in a harness under the rug in the rear storage area just behind the rear driver's side tire. I did not have 12V here. Ok, so move forward some more. Found the harness under the driver's side door sill, it appeared intact so I visually checked it and followed it to a connector under the dash by the left kick panel where I found the issue. The light green wire on the dash side of the connector was completely severed... it was very close to the clutch pedal and likely was severed by the operation of the pedal. This also explains why the fuse was only blowing while driving...each time the clutch pedal was operated the exposed live end of the light green wire was shorting to the arm of the clutch pedal!

Repaired the wire with a nice soldered connection and resecured the entire harness up an away from the clutch pedal. Backup lights work


Side note - the steering wheel issue was a mix of things. The wheel was off 180* while driving straight. I pulled the wheel and found the wheel hub mounted 90* out from the mark on the steering shaft. I corrected this and the cancel cam and remounted the wheel. No with the wheel pointed ahead the wheels were turned quite a bit (the remainder of the 180*). I put it up on the alignment rack and found each side off by about 5*. I had plenty of adjustment to bring it into spec, and the wheel now points straight with the wheel straight ahead

Side side note - While doing the alignment I found a deep gouge on the inner sidewall of the passenger's side tire. Found the outer tie rod rubbing real bad. It looks like the passenger side steering knuckle may be bent. I have a separate thread for this if you want to follow that repair.