Check all the ground wires. IIRC, there should be:
- Very important - Instrument panel ground, black wire up under the dash, often grounded to the emergency brake bracket
- Front Lighting harness - black ground wires on each side of the engine compartment on the radiator support. Passenger side wire should also ground to the battery negative.
- Battery ground (large wire) from the battery to the alternator mounting bracket
- Engine ground from block to frame on passenger side, usually a flat braided wire
- Engine ground from block to firewall on passenger side, should be a smaller sized braided wire
- Ground for rear lighting, in back under the bumper - large gauge white wire coming out of lighting harness
- Each tail light and parking light is also grounded, usually with a white wire. Bad ground will usually only affect one bulb, or in the front it may make turn signals flash incorrectly
Interior lights coming on at the wrong time is a definite grounding problem. They work differently because they have constant 12 volts power, but are turned on when grounded through the door switches or by rotating the headlight switch. This is the opposite of most other bulbs and devices, which are always grounded, and then turned on by applying power.
Bruce
