Defective headlight dimmer switch

A defective headlight dimmer switch can prevent the switching from high beams to low beams. Depending on the nature of the defect, the beams may not be able to be switched. For example, if the high beam circuit is shorted, the headlights will always uses high beams.

Table of Contents

• 1. Symptoms
  • 1.1 High Beams Always On
  • 1.2 High Beams Won't Turn On

Symptoms

One key factor to note is the lack of changing from high beams to low beams. If switching to high beams causes the lights to turn off, the problem may lie with the bulbs or headlight relay, not the dimmer switch. The same goes for low beams.

High Beams Always On

If the headlights are always on high beams, the dimmer switch may be stuck completing the high beam circuit. In this case, the headlights can turn off and on, but the current will always flow to the high beams rather than the low.

The high beam circuit may also have a short so that the electrical current bypasses the relay and illuminates the high beams.

High Beams Won't Turn On

If the high beams won't turn on, and the low beams remain on, the dimmer switch is not changing the circuit. Another possibility is that the low beam circuit has a short so the electrical current is bypassing the dimmer switch.