I have an issue with my Reverse Lights. I have a good fuse, and known good lamps.
I pulled the lamps and found that I have 12v at the sockets. The circuit design is a bit odd, the reverse switch feeds the left side lamp assembly, then jumpers out on another pin over to the right side lamp assembly. I get voltage at both lamp sockets when the lamps are both removed. But, when I insert either lamp, the voltage drops to 0.
Voltage applied is a function of the load on the circuit, so I have decided that I have a very dirty reverse switch on the transmission -- it's a manual trans, by the way. The switch passes 12v, but has very high resistance, which lowers the current available in the circuit. When the bulbs are inserted, the load exceeds the available current, and the voltage drops to
The tail lamp assemblies share a common ground, and none of the other lamps are giving me trouble, and I can connect the reverse lamps directly to the wires that give them 12v and ground, removing the bad ground scenario from the equation, and the lights do not come on. I can plug the lamps into other sockets, and they work fine.
If I connect my volt meter properly, it can tell me the current that is available -- I haven't done this test yet. I would expect to see something in the range of 10 amps (this is the rating of the fuse) to make the lamps come on. If I only see 0.5 amps, this would seem to support my theory of a bad switch. Is that right? Any other ideas?