Dashboard Lights Not Working When Headlights On: Troubleshooting Guide

You flip your headlight switch to activate the front headlamps, only to notice the dashboard instrument cluster remains dark instead of lighting up. This frustratingly common problem leaves drivers needing help to watch speed limits and gauges on nighttime roads.

In this comprehensive troubleshooting guide, we’ll dive into the intricacies of the dash lighting circuitry and its interrelationship with your headlight switch. You’ll gain critical insights into the automatic electro-mechanical processes that should illuminate the dash upon headlight activation.

Understanding how activating the headlamps should also power the instrument panel lighting allows a smarter diagnosis of electrical faults. We’ll provide focused troubleshooting tips to determine if the root causes stem from simple issues like bad bulbs and blown fuses to more complex wiring faults and switch failures.

Possible Reasons Of Dashboard Lights May Not Come On When Turning On Headlights

Faulty headlight switch

• When headlights are on, the headlight switch makes contact to send power to dash bulbs. 

• If connections are not stable inside the button, lights may not engage.

Blown dashboard light bulbs

• Burnt-out individual instrument cluster bulbs like a speedometer or gauge lights will prevent illumination in affected areas.

Disconnected or damaged wiring

• Wires from the headlight switch to the dashboard bulbs can shake loose or get cut over time.

How to Test Car Wiring with Multimeter

Open lighting circuit fuse

• A dedicated fuse often supplies power to the instrument panel lighting. 

• If this fuse is out of shape, it cannot work correctly and disconnect electricity to the cluster.

Faulty dimmer control

• The rheostat that adjusts dash light intensity could fail in a way that prevents any power from reaching lights.

Loose or dirty ground connection

• Dashboard bulbs rely on proper chassis and engine grounding. 

• Loose battery cables or corroded ground points may interrupt the ground path, which results in a dark dashboard while turning on the headlights.

Failed circuit relay

• The relay is responsible for engaging dash lights when headlights turn on. 

• If these circuits are faulty, they could malfunction and not close their internal switch to light the cluster. 

Damaged multifunction switch

• On some models, a defective combination turn signal and headlight switch prevents lighting the dash when headlights are activated.

Solutions For Troubleshooting And Fixing Dashboard Lights That Do Not Turn On When Headlights Are Activated

Inspect and replace any burnt-out instrument panel bulbs

• With headlights on, systematically check every dashboard light bulb for illumination. 

• Replace any bulbs that are not lighting up using the correct OEM bulb types.

Test headlight and dimmer switch function

• Use a multimeter to check for continuity when toggling the headlight and dimmer switches. 

• Also, wiggle switches and wiring to check for loose connections or wire breaks. Replace if you find any faulty switches.

Examine the condition of the wiring harness

• Carefully inspect the wiring from the headlight switch to the light bulb sockets by looking for rubbing, cuts, loose pins, or corrosion that could cause openings. Repair or replace if you find any.

Verify electrical ground connections

• Confirm chassis, engine, and battery ground straps are clean and securely fastened. 

• Check ground-related connections to lighting circuitry specifically.

Check for blown dash light fuse

• Locate the fuse box and inspect the fuse, which is designated for instrument panel lighting and test it for continuity. 

• If you find any faulty fuses, replace them to overcome the issue.

Reseat dashboard wire harness connectors

• Gently disconnect and reconnect wire harness plugs, which are related to cluster power, to clean contact surfaces and to seat connections firmly.

Scan for computer diagnostic trouble codes

• Use an OBD2 scanner to check for logged body control module fault codes that are pointing to open circuits or component failures.

Test operation of headlamp relay

• Relay contacts can wear over time, preventing the activation of lighting circuits when headlights are on. 

• Therefore, replacing the headlap relay is essential if worn out.

Frequently Asked Questions About Dashboard Lights Not Working When Headlights On

Q: Could an electrical short cause my dashboard lights to not to turn on properly?

A: In rare cases, short circuits can bypass and turn off dashboard lighting circuitry. However, more common reasons are open circuits, but shorts leading to grounds should also be under investigation.

Q: How urgent is it to get my dashboard lights repaired for nighttime driving?

A: Restoring cluster lighting for safety, visibility, and awareness of speed and engine vitals at night is highly urgent. Use a phone assistive light or flashlight temporarily with extreme care.

Q: Are there any quick fixes I can try to get the dash lights working again?

A: Unfortunately, dashboard illumination issues require a proper electrical diagnosis. But checking for bad bulbs, testing switches and fuses, and exchanging relays may yield quick fixes.

Q: Can dashboard lights stop working intermittently even when lights are on?

A: Yes, loose wiring and faulty switch contacts can create situations where dash lights flicker or briefly cut out when headlights are activated. This signals an impending failure.

Q: Will a dash light repair be covered under my manufacturer’s factory warranty?

A: If the vehicle is still under the 3-year/36,000-mile bumper-to-bumper warranty period, then the manufacturer would cover any related repairs for electrical lighting issues.

Q: Can I troubleshoot dashboard lighting problems by myself, or are repairs best left to professionals?

A: If comfortable diagnosing electrical issues, begin with basic bulb, fuse, and switch tests. For advanced diagnostics on shorts and opens, an auto electrician is ideal.

Q: My dashboard lights only work when I manually hold the dimmer switch – what should I check?

A: This points to a bad connection in the headlight switch or dimmer. Carefully inspect terminals and wire connectivity. Because intermittent contact equals impending failure.

Q: Why does my mechanic say first to check ground connections if my dash lights aren’t working right?

A: Proper grounding is essential for completing the light circuit. Corrosion on ground points increases resistance, which results in preventing lights from activating when headlights turn on.