I have replaced the turn signal switch and the wiring harness from the firewall all the way back to the rear lights. After doing this, things got weird. When I turn a blinker on, both lights flash. When I turn the turn signal switch off, they keep blinking (rear tail lights). I tried to contact Classic Parts by e-mail asking if it was possible that the turn signal switch might be bad, but received no reply. So, I thought it could possibly be the underdash wiring harness and just finished replacing that. Still the same problem. Any Ideas? Thanks
You should start checking circuits using a probe light. Auto parts store carries them. Looks like an ice pick with with a wire and clip attached. Start at the column harness and with a wiring diagram in hand start checking circiuts on the dash harness connector side of the harness. Turn the left signal, and make sure that the harness wire is connecting to the dash harness wire it's supposed to be. Work your way through all the circuits. If that looks OK, then repeat with the cab harness connectors until all the wire is verified as going to their proper destinations. It sounds like a combination of crossed wires and bad ground somewhere... dv
