[Early_S_Man]

Mike,

This problem is usually a combination of mud and water leakage into the rear lamp housing. So, my suggestion is to unplug the 6-pin bulkhead connector, and remove the housing from the car. Clean the complete wiring harness with Windex or a similar cleaner, then move to the interior and lamp sockets. You can test the lamp housing with multimeter from the bulkhead connector pins, beforehand, if you wish, but the visual evidence is usually clear enough! When all of the dirty cleaning is done and the short(s) are gone ... rinse all connectors and sockets with 90% isopropyl alcohol. After drying is complete, test the circuits again with bulbs and fuses, and if all test OK, put silicone grease on the bulkhead conne4ctor pins and reassemble.

If the problem isn't the rear lamp, do the same procedure with the front lamp assembly. Good luck!