Join Date: Mar 2016
Location: Lake Mary, Florida
Re: BU Light ?
I went through this a few months back, having to install a missing neutral safety switch on my floor shifter (automatic transmission). If you remove the 4 screws that hold down the two half pieces that surround the shifter's shaft, you should be able to see the neutral safety switch to the drivers side of the shifter's base shaft. There will be four wires connected to this switch; two large guage purple wires, which are for the starter voltage, allowing the engine to start in Park or neutral only. Then there will be a smaller red and green wire; these are used for the reverse lights. The red is 12 volts, and the green wire runs (eventually) to the back tail light housings to provide power to the reverse light bulbs.
With the key in the "run" position (no need to start the engine), verify there is 12 volts at the red wire. If so, move to next step, which is to put the gear selector to the "R" (reverse) selection. The green wire should have 12 volts now. If not, wiggle the shifter front to back a bit to see if the neutral safety switch contacts are dirty (inside of the switch). If you get 12 volts at the green wire at the nuetral safety switch location, the fault is after the switch. If you don't see 12 volts at the red wire, fault is from red wire to fuse panel. If you have 12 volts at red lead, but not at green lead with selector in reverse, and ignition key in the run position, then the neutral safety switch is suspect. This switch can be removed, and there are 4 tabs that can be carefully bent back to allow you access to the copper contacts inside the switch. Clean them with some fine sandpaper, apply a smear of grease on the copper, then reinstall its cover, and use a volt/ohm meter to check for continuity at the two contacts that are for the reverse light wire connections, and also the starter connectors. Reinstall the switch. Test again.
If the neutral safety switch checks out good (12 volts at green wire when the shifter is in reverse and ignition key is in the run position), then fault is within the green wire to rear of tail light assemblies. Check that the reverse bulbs are good, and that you detect a good ground at these two bulb sockets. The 67 tail light assemblies obtain their ground using 4 "bumps" of the tail light assemblies making good contact with the body. You would have to remove each tail light assembly from the car to see these. Since the other rear lights are working (brake, turn signal, and running lights), the ground is assumed good though at this location.
Never argue with an idiot; they'll only drag you down to their level, then beat you with experience.