Originally Posted by k2enemy
When I turn my right or left blinker on both blinker lights come on and stay on, the speedo and tac lights flash and both outside turn markers flash. It does the same with the lights on too. Where do I start? There is no reason to believe any wiring is mismatched, how does this even happen?
Make sure that you have the right lamps installed for the turn signals. If 1156 (single center contact base) is installed rather than the 1157 (dual contact) then the 1156 will short the two contacts in the base connector together and cause the voltage to back feed through these circuits and cause this very symptom. Easy thing to do as these lamps are identical in every way other than the single or dual filaments (contacts). This may not be the cause of your problem, but should be ruled out before chasing grounds.