Backup Lights Not Working

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Ricks70Duster340

Ricks70Duster340

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I replaced the NSS on my 70 Duster because the old one was leaking fluid out. Found the backup lights are not working but not sure if they were working before replacing the switch. I have the wiring diagram but need to know where to start troubleshooting the issue. Thanks for the help guys.
 
I would start at checking bulbs. With ignition switch on, shifter in reverse you should have power at the bulb sockets. If not, go to bulkhead connector and check for power going down to the NSS switch. If you have power going down and NOT coming back, the problem is at the NSS. If you dont have power going down, the fault is inside the car, fuse maybe.
 
The switch has 3 terminals. Reverse lights the switch jumps the two outer terminals of the switch. So remove the switch connector and with key in "run" see if you have power to one of the outer terminals. If you have a helper, jumper a short wire across the two outer terminals and see if lights work.

As suggested, otherwise check bulbs, and with key "on" and in reverse, check for voltage at bulb terminals.

You have a shop manual? Download one free from MyMopar. No I don't work there
 
67Dart273 said:
The switch has 3 terminals. Reverse lights the switch jumps the two outer terminals of the switch. So remove the switch connector and with key in "run" see if you have power to one of the outer terminals. If you have a helper, jumper a short wire across the two outer terminals and see if lights work.

As suggested, otherwise check bulbs, and with key "on" and in reverse, check for voltage at bulb terminals.

You have a shop manual? Download one free from MyMopar. No I don't work there
Click to expand...
yep, I didn't want to send him back under the car or under the dash right away. Some testing can be done under the hood, at bulkhead connection. I have pulled the connector off the 3 pin NSS switch and used a cotter pin to jumper the 2 outer contacts.
I recall one case where everything was good except sifter linkage adjustment. The trans was in reverse but adjustment was off just enough to open the switch. Reverse lamps blinked on and off again as shifter moved. A helper came in handy there.
Neutral is a wider detent so we can wiggle the shifter there and get neutral safely to work. Park and reverse are a lot tighter and need to be on the money. Worn bushings in shifter linkage, failed/sagged trans support, etc.. can adversely effect this adjustment. Lowering the steering column for some other issue in column shift builds is even more common loss of linkage adjustment.
He didn't say it wont start in park but does start in neutral so maybe linkage adjustment is not the problem. New switch doesn't mean good switch today.
There was another thread here where the owner had a replacement switch that was just a little bit longer than the one he removed. It worked only once and failed. Took it out again to find it broken. Good luck to all.
 
Do not forget Basic Linkage adjustments!

Just a tad off and you think all is well cause Park and Low work!
 
Thanks guys. I will try the suggestions mentioned and report back the fix I find. The car is an automatic with a B&M floor shifter.
 
When I had the trans rebuilt, I replaced the neutral safety switch. I assumed the switch was good (was a new NAPA Gold part). Well, on a whim, I ordered a NOS NSS from EBay and that resolved the issue. So much for "gold" parts.
 
Ricks70Duster340 said:
When I had the trans rebuilt, I replaced the neutral safety switch. I assumed the switch was good (was a new NAPA Gold part). Well, on a whim, I ordered a NOS NSS from EBay and that resolved the issue. So much for "gold" parts.
Click to expand...
Yep, We have seen a few threads about replacement 3 prong/dual function switches from aftermarket. Evidently there was a slight change in the depth of the switch nose. Happy moparing
 
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