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High Beam Indicator Flashing on Dash While Low Beams Are On (Peterbilt)

A Resistance Mismatch Is Causing the False Indicator Here Is the Fix

If you have installed JW Speaker LED headlights on a Peterbilt 389 or similar commercial truck and the high beam indicator is flashing while your low beams are on — even though high beams are not engaged — this is a resistance issue between the LED headlights and the truck's electrical monitoring circuit.

Why it happen

Commercial truck electrical systems use circuits that monitor current draw to confirm which lights are active. LED headlights draw significantly less current than the halogen lights the truck was originally wired for. When the monitoring circuit detects low current on a circuit it expects to see active, it can generate a false indicator signal.

Diagnosis

Before troubleshooting further, confirm the LED headlights are the cause.

Temporarily reinstall the factory halogen headlights. If the flashing indicator disappears with the factory lights in place, the LED headlights are confirmed as the source of the issue.

Solution: wiring a load resistor

A load resistor wired in parallel with the headlight circuit simulates the higher current draw of a halogen bulb. Once the monitoring circuit detects the expected current level, the false indicator stops.

Mounting: Load resistors generate significant heat. Mount them away from heat-sensitive components — metal brackets, frame members, or purpose-built heat sinks are appropriate locations. Never mount on plastic or near fuel lines.

Sizing: Consult an authorized JW Speaker dealer or a qualified truck electrician for correct resistor sizing for your specific Peterbilt model and wiring configuration.

Also check: wiring harness

Confirm the JW Speaker wiring harness for your Peterbilt model is correct and fully seated. A mismatched harness or loose connection can also cause unexpected indicator behavior.

Next steps

  1. Reinstall factory halogens temporarily to confirm the LED headlights are the cause
  2. Contact an authorized dealer or qualified truck electrician for load resistor sizing
  3. Verify the wiring harness is the correct model and fully seated

Find a distributor: https://www.jwspeaker.com/dealers/distributors/