Neutral safety switch?

-
19blockhead72

19blockhead72

Well-Known Member
Joined
Sep 10, 2016
Messages
271
Reaction score
95
Location
Gettysburg pa
Had an occasional no start latey. It a 74 small block Dart with factory harness. I turn the key and nothing. I can jump it at the relay no problem. Replaced the relay twice but have original neutral switch in the tranny. Whats a good way to check that and best place to get one thats not Chinese junk. Thanks
 
74 model has a one year only seat belt interlock feature also. Majority of those have been bypassed today but how/where it was bypassed may be a factor. That is the first place I would look at 74 model.
For the starter relay to close and run the starter, it needs 12 volts on a yellow wire when ign' switch is in start position ( interlock would interrupt this 12 volt path ) and a ground path via the brown wire through the neutral safety switch when the shifter is in park or neutral. A simple test light ( and maybe a helper at the switch ) should be all you need to diagnose.
 
RedFish said:
74 model has a one year only seat belt interlock feature also. Majority of those have been bypassed today but how/where it was bypassed may be a factor. That is the first place I would look at 74 model.
For the starter relay to close and run the starter, it needs 12 volts on a yellow wire when ign' switch is in start position ( interlock would interrupt this 12 volt path ) and a ground path via the brown wire through the neutral safety switch when the shifter is in park or neutral. A simple test light ( and maybe a helper at the switch ) should be all you need to diagnose.
Click to expand...
Ok good info. So for the nss just put a jumper to ground?
 
well... You could just jumper the brown to ground at the relay but... the starter would work/run with trans in any gear, safety lost.
 
On my 74 the NSS switch has three pins one for the neutral part one for the backup lights and one is the ground, just use a ohm meter and check the nss part of the switch the brown wire to the ground pin which I think is the middle pin if I remember right,
 
Any chance you changed the tranny? Also I have a few good used three pin switches if needed.
 
There have been many cases where the steering column was lowered to service the inst' panel, etc..., and where there was a column shifter, lowering the column altered the shifter linkage adjustment. In these cases wiggling the shifter would change a no start to start. So changing the trans is just one of many possible scenarios.
If you want to crawl under the car with ohm meter, the brown wire NSS circuit is the center pin of that switch.
 
Thanks red for got which pin it was, mine has a new trans and it hat the wrong rooster tail in it for the year, had to put a button on it for the back up lights to pass inspection! Freaking Jeggs, told them I needed a 74 trans! I am done with them for sure.
 
halifaxhops said:
Any chance you changed the tranny? Also I have a few good used three pin switches if needed.
Click to expand...
The car is a full build. Rebuilt trans, new engine ect. Yes its a 3 pin, two for reverse lights and the other is the nss. It wasn't working when I fish went to fire the car 2 months ago. Bought one from napa that broke right away. Got another that didn't work out of the box. Messed with the original and got it working. Now I think its failing again . Might be interested in a good used one, I'll let you know.
 
The way to jumper around the seat belt thing (does not affect NSS) is to find the big red reset button device under the hood. It will have two yellow-ish (with tracer) wires going to the relay which are the "start" circuit feeding TO the start relay. Jumper permanently around these.

Wiggle the shift lever from P--N as you try and start if it clicks or cranks you are in the right area.........either bad switch, loose/ misadjusted linkage, or problems internally
 
67Dart273 said:
The way to jumper around the seat belt thing (does not affect NSS) is to find the big red reset button device under the hood. It will have two yellow-ish (with tracer) wires going to the relay which are the "start" circuit feeding TO the start relay. Jumper permanently around these.

Wiggle the shift lever from P--N as you try and start if it clicks or cranks you are in the right area.........either bad switch, loose/ misadjusted linkage, or problems internally
Click to expand...
This seat belt thing Ill have to look into. I don't have a relay with a nig red button but there is one that just a small silver relay. The seat belt plugs aren't hooked up and haven't been fo 28 years.
 
19blockhead72 said:
This seat belt thing Ill have to look into. I don't have a relay with a nig red button but there is one that just a small silver relay. The seat belt plugs aren't hooked up and haven't been fo 28 years.
Click to expand...

The reset box is under the hood, about the size of a horn relay

100_0894-jpg.jpg
 
Alright I was wrong and you guys were spot on. I do have that relay, it how ever was painted over. Jumped the two yellows together and bam! Thanks soooo much!
 
Great!! Without a doubt that interlock was one of the Fed's more stupid ideas. Be interestin' to know how many folks were needlessly stranded with those damn things, either tripped doing their job or failed
 
19blockhead72 said:
The car is a full build. Rebuilt trans, new engine ect. Yes its a 3 pin, two for reverse lights and the other is the nss. It wasn't working when I fish went to fire the car 2 months ago. Bought one from napa that broke right away. Got another that didn't work out of the box. Messed with the original and got it working. Now I think its failing again . Might be interested in a good used one, I'll let you know.
Click to expand...
Any chance your back up lights just come on? (that was one of my issues with the wrong comb)
 
You must log in or register to reply here.
-

Back
Top