NSS diagnostic question

[str12-340]

Out around town in my 1970 Dart (340, auto) yesterday I stopped for a snack and a drink and when I came out and I turned the switch - nothing happened. I fiddled around with the shifter and tried Park and neutral, but no dice. I figured that the NSS plug on the trans had come undone, crawled under the car and nope it was snug. I went under the hood to look if something was obvious, nope. So I turned the key on, took a screwdriver and jumped the solenoid and it started right up and ran with no problems a few miles home. I again tried the plug at the trans, pulled it out and snapped it back in place. I traced the subharness from the NSS to the bulkhead connector, even pulled the bulkhead plug and everything looks fine. I even pulled the starter solenoid off one of my other Darts and installed it with still no results.

I'm starting to think that the NSS in the trans is shot (god knows how long it's been in there). If I pull the plug, I assume that I can bypass the NSS and see if the car starts and if it does replace the NSS. Does all this sound logical, or am I missing something obvious?

Is it correct that this is just a matter of screwing the old NSS out and screwing a new one in?

Thanks for the help.

 

[dadsbee]

Pull the wiring socket off the switch. Stick a wire in the CENTER socket connection and ground it out to the frame. If it starts the switch is shot. If not it's in the wiring.

 

[67Dart273]

^^That is a good plan.^^ This is a VERY simple circuit. The functional path is from ignition switch in start, out the (usually yellow) "start" wire---through the bulkhead connector---to one flag "push on" terminal of the start relay, whichis the magnetic coil. Through the coil, out the remaining flag terminal, to the wire running down the firewall to the center pin of the NSS. When in N or P the switch should be grounded, completing the circuit

What can be wrong in no particular order:

Bad key switch, bad connection at switch connector, bad connection through bulkhead connector, bad start relay, bad connection at NSS, bad NSS.

Shifter / linkage out of adjustment, and sometimes, problems internally in the transmission with the roostercomb.

If this is intermittent enough that you have trouble pinning it down, another thing I'd try and BE CAREFUL--is to temporarily make up a wire with a female flag terminal and ground the start relay NSS terminal. This bypasses the NSS, and if it does not give more trouble, you can concentrate on the NSS and it's wire, etc

 

[dadsbee]

I should add, it could also be the rooster comb inside the trans that's not making the NSS function properly, but at least verifying whether it's the wiring or switch mechanism is the first step.

 

[str12-340]

sounds like the wiring or the switch. It failed without warning and hasn't worked at all since. I've moved all of that wire all around looking for a short from bunged insulation or something and it hasn't turned over at all, so chances are not the wire (though I'll check again). If I ground the middle terminal in the plug and all is well I'll pull the switch, take a good look inside while changing the gears by hand and if all looks good replace the switch. It seems like a switch thing somewhere because it just failed out of the blue and hasn't bumped the starter since. Sure hope it's not the relatively new column switch, I hate getting in there again after rebuilding the whole thing 3 years ago.

 

[str12-340]

you learn something new every day. I was tracing out the wiring in the FSM and discovered that while this has been a Neutral Safety Switch to me for decades, Chrysler says it is a Neutral Start Switch...

 

[sabre67]

 

[Murray]

Easier- jump wire the NSS wire at the relay to ground.If that fixes it then your problem is relay/wiring/NSS.

 

[cudamark]

Yup, pull the NSS wire off the starter relay and replace it with a jumper wire from the terminal to ground. If the car now starts, it's going to be the wiring down to the NSS, the switch itself, or, an internal transmission problem. If the car still doesn't start with the key, check to make sure you're getting 12V juice to the starter relay wire from the ignition switch in the start position. As mentioned, make sure the transmission is in Park/neutral and the E-brake is fully engaged, or rear wheels off the ground when doing these tests.