As much of a PITA it would be to run around chasing wires, just throwing a sensor at it and hoping for the best will not solve your problem.
IMO, replacing that wont do a thing. If your brake lights illuminate when you hit the brake pedal, that switch is fine and you're doing yourself no good to replace it. You're most likely culprit is a short to ground and its overloading the circuit.
This is a simple circuit. I'm assuming a 5-speed, if that is wrong, then the only difference is in the switch.
The short has to be between the switch and the backup lights. If it were in front of the switch, it would always be shorted and you would not see the symptom you are seeing.
Look at the backup lamp switch. Should have a purple/orange wire going in, and a black/pink wire coming out. That wire goes to the back of the car and powers the backup lights. I would be tempted to start at the backup lights themselves and check the lamp sockets and the wire coming out of the socket to make sure that all looks reasonable.
I'd start like this:
1. visible inspection of the lamp sockets.
2. Next take an ohmmeter and connect to the black/pink wire at the reverse lamp switch, connect other probe to ground (easier if you remove the backup lamp bulbs). Circuit with bulbs out should be an open circuit, infinite resistance. With bulbs in, it will not be open, the resistance you read will be the resistance of the bulbs which will make it more confusing. Remove 'em. If you find 0 ohms you now know that between the switch and the lamp socket there is a dead short to ground.
I am not sure how the wiring goes between the two lamps, but it probably comes in on one side of the trunk and runs all the way across to the other lamp. Anywhere along that path is a potential problem.
If you remove the lamps and get an open circuit, you could have a bulb with an internal short. Or you might have opened the circuit when you wiggled the wire, again letting you know that the short is "close by".
Best bet is right around the socket or else where the black/pink wire comes out of the "bundle" and goes to the light assembly.
Do you guy's happen to know if this is a reverse polarity curcuit (or whatever it's called). Meaning, does the hot lead run through the bulbs, THEN to the back up switch? Instead of to the switch, then bulbs, which would make sence. Base on what you're saying, it's not reversed. I have this same problems with my 94 auto V6 convertible. Same curcuits I'm sure, except the around the tranny. My problem is the fuse WILL ALWAYS blow out with a hot engine (in foward, reverse and park). And it WILL NEVER blow with a cold engine (also in any gear). I have already removed most other things on that curcuit (air bags, air bag module, turn signal switch, rear defroster switch, rear defroster harnesses at the back window, center console with convertible switch, and AOD override).
MustangX, I'll keep you posted on everything I find. We might be dealing with a chafed or crimped wire, or god know what else, in the same location.
MustangX, I'll keep you posted on everything I find. We might be dealing with a chafed or crimped wire, or god know what else, in the same location.
Let me make sure I understand. First, remove the tail lamps. Now try the test by putting it in reverse. Does it blow? If so, you know the short is between the bulb and the switch or the switch and the front of the car (so far as I know, the +v comes from the front of the car, thru the switch, to the lamps and then to ground in the rear.
One thing I did not mention, the switch itself can be bad. You could verify this by using a jumper to connect the switch connector from the front +v source to the switch, but do not connect the other pin to the black/pink wire going back to the lampa. If it blows now, the switch itself is bad and should be replaced, as it is responsible for grounding the +V. Again, I like to confirm before buying, so you can do this:
Unhook the connector and take your ohmmeter and connect it to the +v pin (not the black/pink wire). Connect the other probe to ground. In park you should be seeing "open circuit". Now shift into reverse. If it goes to 0 ohms, it is shorting +v to ground inside the switch and the switch is bad. If it passes that test, swap the ohmmeter to the other pin and do the same test. Again, you should never see 0 ohms. If either pin gets shorted to ground, replace the switch and your problem will be fixed. If not, you still have to have a shorted connection from the switch on back.
Already a step ahead. 04 Red GT Convertible. It's already parked in the old Mustang's spot. I just spent 9 hours cleaning, detailing, and waxing the old one. I'm gonna take some pics and put it on craigslist tomorrow. It's too dark for pics now. That thing better be shiny as hell when the sun comes up. 9 freakin hours.
purple/orange into the switch. black/pink out of the switch to the tail-lamps and on to ground.
Really sounds like the switch itself might be the culprit... Clearly it is the switch or farther back.... Also I don't know how your tail lamps look, but I just worked on a GM1500 that had a set of lamp sockets on a circuit board, and there was a nearly invisible short on the circuit board itself that was making the backup lights turn on the tail lamps...
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