This'll be a real PITA to check, but...
The headlight switch, wiper switch, cig lighter and gauge cluster assy. are grounded by 2 tin stampings that are trapped between the switches and the dash housing plastic. The driver's side (headlight & wiper) achieve ground through the left-most upper bezel mounting screw. The cig lighter (and cluster again) achieve ground through the radio chassis & rear radio support mount.
It's a pretty weak design - the dash screw loosens/rusts and you lose that ground, put in an aftermarket radio (cutting the dash & altering the tin stamping) and you lose that ground.
Run a dedicated ground wire (18ga) using some ring terminals from one of the instrument cluster to bezel screws (1/4" hex heads - on the metal cluster) to the body sheetmetal above the E-brake. This usually solves a myriad of flaky dash problems. Also tighten all the dash bezel holddown screws, and headlight/wiper switch attaching nuts.
The headlight switch, wiper switch, cig lighter and gauge cluster assy. are grounded by 2 tin stampings that are trapped between the switches and the dash housing plastic. The driver's side (headlight & wiper) achieve ground through the left-most upper bezel mounting screw. The cig lighter (and cluster again) achieve ground through the radio chassis & rear radio support mount.
It's a pretty weak design - the dash screw loosens/rusts and you lose that ground, put in an aftermarket radio (cutting the dash & altering the tin stamping) and you lose that ground.
Run a dedicated ground wire (18ga) using some ring terminals from one of the instrument cluster to bezel screws (1/4" hex heads - on the metal cluster) to the body sheetmetal above the E-brake. This usually solves a myriad of flaky dash problems. Also tighten all the dash bezel holddown screws, and headlight/wiper switch attaching nuts.