Volvo Repair: Tail lights, volvo 240, electrical contact

Question
Hi Pat. I have a '91 Volvo 240. I am the only owner. My tail lights on the driver's side went out but the passenger lights work just fine. About a week ago the passenger side lights went out and came back on and continue to work fine. The other side is still out. I checked the bulbs and fuses and all are good.

Answer
Hello Al,  The most likly cause may be the connectors at the circuit boards.They can get loose and the ground wire(black wire) turns dark and burnt also the electrical contact for the bulb socket wear off.Check them both.Thank you and good hunting!  PKD