My 99 Town and Country blows the backup light fuse when put in reverse or when driving on the highway for an extended time. The reverse fault is constant in reverse and stays during the highway driving until the car is stopped and put in park. This clears the problem for another hour or two. Because of this, I don't think it is the backup lamp circuit. The same fuse powers the ABS controller, turn signals, and front air conditioner fan. I rigged a circuit breaker until I can solve this problem.
I assumed it was the switch in the transmission but since it is inside the tranny behind the valve body, I paid a transmission shop $200+ to replace it without any resolution. They called the part a Prindle switch and it appears to signal all gear positions through a group of 4 spring loaded contacts. Since this was not a complete switch, I asked the shop for the moving part of the switch and was told that was all there was. The tech said the moving part was all steel, not an insulated set of contactors I would have expected. I did not see it so I cannot be sure of his response.
Thanks for any help.