Changing neutral safety switch
Well that was frustrating. I replaced the switch (Standard Motor Products NS-11) without much fuss but still no backup lights, which was the problem. The NSS function of the original switch was ok. I had jumpered the two outer pins of the wiring connector and had backup lights, so it had to be either the switch or the actuator inside the transmission, which seemed unlikely.
The old switch bench-tested bad and the new one good. The backup function is a normally-closed switch that has continuity when the plunger is extended, and the actuator pushes it in for all shift positions except Reverse. But installed in the trans, the switch had no continuity in any shift position, which suggested a misadjusted actuator or the switch extends too far into the transmission.
So I unscrewed the switch a little at a time, checking for continuity. At two full turns out the switch closed. I removed it and compared it to the old one, and the plastic/metal plunger assembly is 0.08" longer than the old one, preventing it from fully extending when installed. I added a 0.1" O-ring between the switch body and the seal, but it compressed enough that there was still no continuity when installed. Adding a second O-ring allowed the switch to close, but that seems sketchy. I'll look for a single, thicker O-ring. I don't know if all NS-11s are made this way, or if I got one out of spec. Not stocked locally, so I can't measure before I buy.
Sorry for the long-windedness on something so simple. "New doesn't mean good."
Well that was frustrating. I replaced the switch (Standard Motor Products NS-11) without much fuss but still no backup lights, which was the problem. The NSS function of the original switch was ok. I had jumpered the two outer pins of the wiring connector and had backup lights, so it had to be either the switch or the actuator inside the transmission, which seemed unlikely.
The old switch bench-tested bad and the new one good. The backup function is a normally-closed switch that has continuity when the plunger is extended, and the actuator pushes it in for all shift positions except Reverse. But installed in the trans, the switch had no continuity in any shift position, which suggested a misadjusted actuator or the switch extends too far into the transmission.
So I unscrewed the switch a little at a time, checking for continuity. At two full turns out the switch closed. I removed it and compared it to the old one, and the plastic/metal plunger assembly is 0.08" longer than the old one, preventing it from fully extending when installed. I added a 0.1" O-ring between the switch body and the seal, but it compressed enough that there was still no continuity when installed. Adding a second O-ring allowed the switch to close, but that seems sketchy. I'll look for a single, thicker O-ring. I don't know if all NS-11s are made this way, or if I got one out of spec. Not stocked locally, so I can't measure before I buy.
Sorry for the long-windedness on something so simple. "New doesn't mean good."