No Backup Lights & PNP switch

850Cal · Post by **850Cal** » 13 Feb 2017, 20:50

The backup lights stopped working a while ago, and I bought a new PNP switch but never replaced it because I was too lazy to tear it all down. I've got the area torn down now to fix other things and thought it would be a good time to do the PNP. After reading about the alignment and such, I was wondering if it's possible to test the switch before replacing it. If I remove the big connector, what pins can I test to see if the PNP is the problem?

I have already checked the fuse (#27, and it's good) as well as the lamps themselves (also good), so I'm expecting the PNP is the problem. However, rodents have been a real problem in my rural area and I don't rule out a chewed wire is the problem. (They chewed through the wiper motor wires on my Tacoma truck!) I haven't found any damaged wires so far on the 850, but testing the PNP switch would be helpful. Can anyone put up (or link to) the PNP pinout for testing?

Post by **Ozark Lee** » 14 Feb 2017, 17:07

With the shifter in reverse look for continuity between the Blue wire and the Blue/Gray wire on the PNP harness. The pinouts are somewhat vague.

If you have continuity then it suggests the problem is not the PNP switch.

...Lee

850Cal · Post by **850Cal** » 14 Feb 2017, 21:43

Thanks, Lee. I had to put everything together and get the car back on the road, but decided to go ahead and test my known good switch. The blue wires (pins 9 & 4) did nothing as I slowly rotated the shaft on the switch. Extending your logic, I tested the Red pair and then the Green pair, also with no result. I finally tested the White & Yellow wires to pins 1 & 2 and RESULTS! Continuity as I rotated the shaft from the Park position (extreme clockwise lock) back counterclockwise about one "click", then off. The trouble is, I rotated another "click" after that and got continuity again! The circuit was dead again for the rest of the rotation (which I estimate to be another 2 "clicks".)

After all that, I'm thinking the BU lights only need one wire to activate as they are grounded at their mounting point. I'll have to look deeper into this and check back in with some results...