1985 911 Carrera turn signals/brake lights

Vehicle Information: Model: 911 Carrera; Year: 1985; Body Type: Coupe; Engine (type, size, modifications): 3.2; Total Mileage: 138800;

The left front turn signal does not work - the rear one blinks faster than normal. Both right signals work ok. The left brake light works ok - the right one is very dim. The right back-up light does not work.I've cleaned the metal tabs in the sockets - no luck. This means that there is a poor ground somewhere? Would it be in the left front turn signal box? Should I take it out and check for rust or ???I really appreciate the tech Q & A section of the PCA site.Thanks for all of your effort.