Lights turn off when high beams are switched on

Good evening,

This sounds like the dimmer switch.

When the headlights are commanded on, power is sent to the dimmer switch. Then the dimer switch sends power to the headlights based on the command of low or high beams.

The dimmer switch is part of the multifunction switch or headlight switch. I attached a diagram for you of the system.

Roy

Multifunction, Turn Signal Switch Replacement

Removal Procedure

Caution: Refer to SIR Caution in Service Precautions.

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1. Disable the SIR system.
2. Remove the upper and lower trim covers.

Important: The abrasion sleeve located on the steering column wire harness assembly must be reinstalled. Make note of what connector is coming out of the abrasion sleeve for installation purposes.

3. Remove the wire harness assembly (1) from the wire harness strap (2).
4. Disconnect the turn signal and multifunction switch assembly connector from the SIR system coil connector.

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5. Slide the 2 connectors (2) of the turn signal and multifunction switch assembly out of the bulkhead connector (1).

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6. Remove the 2 pan head tapping screws (1) and (3) from the turn signal and multifunction switch assembly (2).
7. Remove the turn signal and multifunction switch assembly (2) from the steering column tilt head assembly.

More then likely it is the high beam or dimmer switch or a wiring issue. If you look at the wiring diagram, the head lamp on off switch is actually separate from the high and dimmer switch. This means that the head lamps are in direct contact through wiring with the multifunction switch/turn signal switch.

The way to test this is to test for continuity between the low and high beam wiring circuits at the headlamp. Then you can unplug the switch to see if the continuity goes away. If not then it is a wiring issue. If it does then it is the switch.

Does that make sense?

You are welcome.

Always glad to help.

Roy