JayEstes 173 Report post Posted April 6, 2015 All, I'm having problems with the backup lights in my car. I have the neutral safety switch installed and adjusted as it does lock-out ignition properly unless in P. The 4 prong plug at the firewall is installed and the harnessing has been checked by mid-life no less, and he put in new fuses too so I have expectation this is not a fuse problem - all my other electrical is working as expected with the exception of the wiper motors which I have not tried. I have had the lights off the car, and when 12v+ applied to the 2 prong harness to each light, they both come on and light up fine. So, I'm not getting 12v out to the back harnesses for them for some reason. What path should I take for debug from this situation? Could it be I don't have the circuit grounded properly somewhere? I figured this is not as a big of a deal for these lights as the harness carries 2 wires (I'm assuming on of them is the ground wire). I'm not sure where the harness gets it ground for these lights, but I probably need to check that. I do have the tail-light harness just laying in the trunk, but to get everything working I am hooking up manual grounds for things like turn signals etc. Any suggestions? Problem seems to be isolated to the reverse lights. Thanks, Jay Quote Share this post Link to post Share on other sites
LoneWolf2U 136 Report post Posted April 6, 2015 The back up lamps get power from the 4 prong trans connector. Power comes from the switched source thru the net switch and back out to the lamps. The lamp socket must be grounded to complete the circuit for the bulb to light. If your net safety switch is adjusted correctly it should show power to the lamp wire feed with selector in R and the ign switch in on position. Quote Share this post Link to post Share on other sites
JayEstes 173 Report post Posted April 6, 2015 It must be the housing ground then... I'll check that later today - I didn't think to ground the housing yesterday when I was working this, so that could very well be it. They are just laying on an insulated surface (padding) in the trunk - with no ground. As you might guess, I am not a "sparky watts", more of a mechanic, so sometimes even this simple electrical stuff trips me up. Even right now, I can't visualize the circuit in my head. And I still wind up asking myself, "why does the bench check of these lights - just 12v from a powersupply - work fine without housing hooked to ground?" Quote Share this post Link to post Share on other sites
LoneWolf2U 136 Report post Posted April 6, 2015 IIRC the back up lamp housing has 2 wire coming from it. you should have a ground wire to attach in the rear loom that provides the grounding for these lamps. Somewhere inside the trunk area. Where these pic's came from I don't know? Quote Share this post Link to post Share on other sites
69volunteer 84 Report post Posted April 6, 2015 That rear loom ground I believe is either (a) at the tail lamps (b) at the license lamp or © both. May make sense to hook those up and see if it solves your problem before going any further. Quote Share this post Link to post Share on other sites
Midlife 814 Report post Posted April 7, 2015 I've seen NSS/BU light switches set properly for NSS but not work in the Reverse position for the backup lights. With the key in ACC, put the shifter in Reverse and have someone watch the rear BU lights. Then jiggle the shifter and see if they come on. I suspect it is an alignment problem. I've also seen many NSS/BU harnesses get pinched when the engine runs (typically a motor mount failing or routing issues) and shorting of the BU lines. Check the top left-hand fuse to see if it is still good. If you can send 12V out back and everything works, then either power isn't coming to the BU side of the plug (female on underdash harness side) or not coming up from the NSS/BU switch (female side on that switch). Quote Share this post Link to post Share on other sites
JayEstes 173 Report post Posted April 7, 2015 Found it. There was a grounding lug (looks like it is near the license plate light) that wasn't hooked up. So, I was right, one of the pair going to the backup light was a ground wire. My trouble was those grounds are both hooked to this ground lug, and without it connected to structure, there was no complete circuit. Really glad it was not the switch. As usual - maybe I am learning idk - it's a bad ground causing problems. Funny I thought I had that covered this time by assuming the ground was in the harness, and I figured harness was golden. Anyway, simple solution.... and I am getting closer! Again, flaky pics showing up at random by the new web-system. Those below were not posted by me, and believe it or not, I can't delete them... Quote Share this post Link to post Share on other sites
