As usual, had the DW test the turn signals and brake lights on the toad just before leaving the RV campground. This time all that would work is the right turn signal and no brakes. The 4 pin round power connector is not that old. I push/pulled both ends and the lights started working. Is there something that I can clean the contacts with and keep them working? I was concerned about them failing while driving.

The easiest way is to use a spray contact cleaner.

An auto parts store will have it.

After a cleaning, you can apply a little dielectric grease to help prevent further corrosion. ACE hardware etc.. sells it

I experienced that problem not too long ago. After several attempts to solve the problem i.e. cleaning and applying dielectric grease, I discovered that I was not getting good contact betwen the male and female prongs. The fit was somewhat loose. I could not do much with the female prongs but I was able to slighly increase the width of the male prongs by enlarging the gaps between the two pieces making each male prongs.

Hope this help.

I had light problems and finally took the cable connectors apart on both ends to check the connections.
Found that 2 screws had loosed and fell out of the pin connector.
Replaced and tightened all screws, have not had the problems since.

Big Red: Hi. I struggled for a year with same problem....then...as Gaetan mentioned, was shown by the RV tech that indeed it was simply the connections being loosed in the electrical plug-in at front of toad. We gently spread those male prongs and haven't had a problem since!!! I'll bet Gaetan is on target with his suggestion. Good Luck. Steve & Lynette

Do not use dielectric grease in electrical systems. It in a non-conductor of electricity.
Use a conductive type grease only.

depchief posted a solution everyone should consider adding to their annual maintenance plan. The screws that hold the wires to the pins, in these cables, are notorious for coming loose. This cable bounces around as we travel.