If one headlight winks, but the other won't, or stays up, or they operate reversed, or neither winks, perform the following checks. Note that these procedures may require removal and installation of the fuses. Be sure to remove them before connecting or disconnecting any electrical components! Failure to do so could result in serious injury! Ensure all warnings are heeded.

• If the headlights wink with left/right reversed, simply reverse the outer wires on the switch (terminals 1 & 3.)
• If one headlight stays up:
  • De-energize the system, swap the black boxes, and re-energize the system. If the problem changes sides, check the affected side black box
  • If the problem is on the same side, then the wiring from the white wire on the 1M5F in-car connector is shorting to ground. De-energize the system, and trace the wire back to the switch, checking for burns through the insulation (from hot engine components), and for cut insulation (from scraping against sharp metal objects.
• If one headlight won't wink:
  • De-energize the system, swap the black boxes, and re-energize the system. If the problem changes sides, check the affected side black box
  • If the problem is on the same side, then the wiring from the white wire on the 1M5F in-car connector is broken. De-energize the system, and trace the wire back to the switch, checking for breaks. Check the splice from the white wire on the 1M5F connector to the switch wire.
• If neither headlight winks:
  • De-energize the system, and remove the tape from the splice between the white wire on the 1M5F connector and the switch wiring on one side. With the fuses still removed, check for continuity to ground while having a friend cycle the wink switch left and right. There should be continuity to ground only with the switch in the left or right position (not both.) Retape the splice. If this check is satisfactory, the problem is in the black boxes.
  • If there is no continuity, check the continuity from the center terminal of the wink switch to ground (use a different ground point than the place you wired the switch to.) If there is no continuity to ground, you must choose a different ground point for your switch.
  • If there is continuity to ground here, check the continuity of the outside terminals of the switch to ground while cycling the switch. (ensure the center terminal (2) runs to the ground and the outside terminals (1 & 3) run to the engine compartment.) If there is continuity from the outside terminal(s) of the switch but not at the white wire in the engine compartment, the wiring from the switch to the white wire on the 1M5F connector must be repaired.
  • If there is no continuity to ground on the outer terminal(s) of the switch, then the switch is faulty and must be replaced.