Help, Neutral Safety Switch

[Duck.E]

All my lights work on the truck except the reverse lights. I noticed the fuse was blown and I replaced it and nothing. So I replaced the NSS and before I put it on I hooked it up and moved the switch and the reverse lights come on. So I thought good, I installed it on the column and blows fuse every time. As soon as I turn ignition it blows, but with switch off it works when I move it. Any suggestions, help? All wiring, harnesses, bulbs, and housings are new.

[ray_mcavoy]

That's definitely a strange problem you have there.

My best guess is that you ended up getting a defective NSS that is shorting the reverse light circuit to the switch's metal backing plate.

With the switch off the column, things worked okay because the backing plate wasn't grounded. But installing the switch grounds the plate to the steering column and that in turn grounds the reverse light circuit and blows the fuse.

To test this theory, remove the NSS switch and use a multimeter (set to the Ohms scale) to check the continuity between each of the reverse light terminals and the metal backing plate. If the switch is good there should be no connection between the metal plate and either of the terminals.

[Duck.E]

Originally Posted by ray_mcavoy

That's definitely a strange problem you have there.

My best guess is that you ended up getting a defective NSS that is shorting the reverse light circuit to the switch's metal backing plate.

With the switch off the column, things worked okay because the backing plate wasn't grounded. But installing the switch grounds the plate to the steering column and that in turn grounds the reverse light circuit and blows the fuse.

To test this theory, remove the NSS switch and use a multimeter (set to the Ohms scale) to check the continuity between each of the reverse light terminals and the metal backing plate. If the switch is good there should be no connection between the metal plate and either of the terminals.

Ok, I will test the continuity tomorrow and let you know the results, thanks for the info. Its a 72 auto, just for more info.

[Duck.E]

Originally Posted by ray_mcavoy

That's definitely a strange problem you have there.

My best guess is that you ended up getting a defective NSS that is shorting the reverse light circuit to the switch's metal backing plate.

With the switch off the column, things worked okay because the backing plate wasn't grounded. But installing the switch grounds the plate to the steering column and that in turn grounds the reverse light circuit and blows the fuse.

To test this theory, remove the NSS switch and use a multimeter (set to the Ohms scale) to check the continuity between each of the reverse light terminals and the metal backing plate. If the switch is good there should be no connection between the metal plate and either of the terminals.

Well after looking at the two switches I noticed the new one was a little different and one of the prongs that is attached to the plate is real close to the edge and sure enough, when I mocked it up to the column it was touching it. So a little grinding took care of it. Now only if I can get my gauge lights to work I think all my lighting issues will be resolved.