On my 71 442 with automatic transmission, I replaced the neutral safety switch . New switch acts the same way. It works once, then it doesn't Adjusting it does not make it work every time. Could the back drive linkage have too much slack in it. I get it working in park , reverse and neutral, then I drive it and it seems to be out of adjustment again.

 

What happens if you jumper the switch when it won’t start? If it starts, you may have to readjust and find a happy medium.

 

Is this a column shift car, a factor floor shift car, or a former column shift car converted to floor shift? Is the backdrive linkage properly installed and adjusted FIRST, then the NSS adjusted?

 

This is a factory duel gate car with stock back drive that has never been changed. The back drive does have some slop in it that could be causing the erratic behavior of the switch.I would not think the switch would be that picky, it would be set for park and reverse, and the rest should line up.The next time it is put back into park it is out of adjustment again. That is why I think there is slack somewhere.

 

1971 model year should have the NSS switch mounted to the steering column. Try this: grab the steering column just forward of the turn signal stalk, and rotate it CCW before starting the car. If this fixes your problem, the back drive linkage is misaligned.