Quick question about the neutral saftey switch

[Ghost's68]

Hello everyone!

I got an LS swapped into a 1968 SWB. The issue I’m having is when I go to turn the engine on it won’t start.

With my power probe I have verified at the time of cranking I am getting 12v to the IGN pin on the ignition switch. I disconnected it at the neutral safety switch and checked to see if the purple wire coming from the switch is seeing 12v which it does.

Does it matter which way I plug the plug onto the posts. I had the top pin going to the started and the bottom pin coming from my switch.

Here’s the kicker, with my powerprobe I am able to throw 12v directly to whatever I’m chexking with the flip of a switch. I am able to start the engine by throwing 12v directly to the top plug. So wiring seems good

Is there a way to test the NSS?

Thanks in advance everyone!

[dmjlambert]

I don't know how exactly you are testing. But here is my suggested testing method:
I'm assuming you have a test probe that looks like a screwdriver except it has a pointy end and lightbulb inside.
With all connections connected where they are supposed to be, connect the probe's ground clip to a good clean ground and then poke the pointed end into the wire coming from the ignition switch. Verify when you turn the switch to start the test light glows. Move the probe to poke the pointed end into the wire coming from the neutral safety switch that goes to the starter. Repeat verify when you turn the switch to start the test light glows. If it glows with the same brilliance at that point, you are not having significant voltage drop across the neutral safety switch. I don't think it matters which connector on the neutral safety switch goes to the starter and which goes to the ignition switch. But you do need to pay attention that you are not connecting to one of the terminals that operates the backup lights.

A different way you can check for voltage drop across a suspected bad device that is supposed to conduct with very little resistance is poke the wire going to the starter with a pin and clamp the ground lead of the test probe to the pin, and then poke the pointed end into the wire coming from the ignition switch. In that case you would verify when you turn the switch to start the test light does not glow at all.

The advantage of piercing the wire insulation for your test is it tests not only the device (neutral safety switch in this case) but it also tests the connector leading to the device.

[VetteVet]

If I might add.
The NSS just connects the two wires when it is closed by the pins on the shifting column shaft in the steering column. So it doesn't matter how the wires are plugged in.The two plug-ins are shaped different so they cannot be swapped. I believe the start wires are one above the other and the back-up light wires are at a 90 degree angle from each other.

What I like to do to see if the NSS is working is to jump the two purple wires in the connector to see if the starter will turn. Make sure the vehicle is in neutral or park.
If the starter turns then all the wiring, the ignition switch,the voltage, etc. is OK and the problem has to be in the NSS. If it doesn't spin then the problem must be in the wiring the solenoid or a connection, and further testing will be necessary. I use a paper clip or a cotter pin to jump the connector.

[Ghost's68]

Update!

I ended up having to adjust the shift linkage to get it to line up. The NSS was doing it’s job thinking the trans wasn’t in park or neutral. Set my continuity checker on the posts and moved the shifter right over the park and it started reading. Tested it and now it turns over. Thanks everyone!