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Home / DTC / B1743 — Hazard lamp fuse blowing out

B1743 — Hazard lamp fuse blowing out

Detailed page for trouble code B1743.

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Code

B1743

MITSUBISHI B — Body

Hazard lamp fuse blowing out

Brand: MITSUBISHI
Type: B — Body
Views: UK: 4 EN: 12 RU: 6
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short to ground in the hazard/turn‑signal wiring (chafed or pinched harness)
  • Faulty hazard switch or flasher/hazard relay with internal short
  • One or more bulbs with internal short or incorrect (over‑wattage) bulbs installed
  • Corroded or water‑ingress damaged lamp sockets or connectors creating a short
  • Aftermarket accessories tied into the circuit incorrectly
  • Damaged fuse holder or poor contact causing arcing and repeated fuse failure

Symptoms

  • Fuse for hazard/indicator circuit blows immediately or shortly after hazards are switched on
  • No hazard or turn signal operation when fuse is blown
  • Fuse blows only when specific lamp(s) or trailer connector are connected
  • Visible arcing, melted fuse holder, burning smell near fuse box or lamp
  • Intermittent operation of indicators/hazard before fuse failure

What to check

  • Confirm correct fuse rating (do not replace with higher amperage fuse to 'fix' problem)
  • Visually inspect fuse and fuse holder for signs of melting, burning or poor contact
  • Inspect all lamp bulbs and sockets (front/rear/side) for corrosion, broken filaments or conductive debris
  • Disconnect hazard relay/ flasher module and check whether fuse still blows
  • Disconnect lamp connectors and trailer connector, then operate hazards to isolate the faulted section
  • Perform a wiring inspection along common chafe points (doors, fenders, rear quarter, trunk) looking for damaged insulation

Signal parameters

  • Typical bulb current: 21 W incandescent ≈ 1.7 A per lamp at 12 V (check vehicle-specific bulb wattage)
  • Hazard circuit total current (all bulbs active) commonly up to ~6–10 A for standard incandescent setups
  • Common fuse rating for hazard/turn circuits: typically 10 A–15 A (vehicle-specific — consult manual)
  • Fuse voltage at supply with ignition on and hazards activated: ~12 V (no more than ~0.5 V drop across good fuse/holder)
  • Ground resistance for lamp circuit: ideally

Diagnostic algorithm

  1. Do not replace fuse with a higher amperage. Replace blown fuse with correct rating to proceed.
  2. With ignition off, visually inspect fuse, fuse holder, and adjacent wiring for heat damage. Disconnect battery negative before major repairs.
  3. Remove all external loads: unplug front/rear lamp connectors and any trailer or accessory connections tied to the circuit.
  4. Replace fuse and activate hazards. If fuse does NOT blow, reconnect loads one at a time (or one lamp at a time) to identify which lamp/connector causes the fault.
  5. If fuse still blows with all lamps disconnected, pull the hazard/flasher relay and retest. If fuse no longer blows suspect relay/module or upstream short near fuse box.
  6. If a specific lamp causes the blow, inspect that lamp socket and wiring for corrosion, water, or pinched wires; repair or replace socket and harness as required.
  7. If fault is not isolated to a single lamp, systematically follow the harness from fuse box toward lamps, using an ohmmeter to check for unintended continuity to ground with the circuit disconnected (fused circuit = remove fuse first).
  8. Use an inline ammeter to confirm current draw when circuit is active; if high current persists with lamps disconnected, suspect short in harness or BCM and consider disconnecting BCM outputs for further isolation.
  9. Repair damaged wiring (replace sections or use proper splice/resealing techniques), replace faulty relay or sockets, and reassemble. Clear any BCM codes and retest.
  10. After repair, perform a final road/test check of hazard and turn signals and inspect fuse holder for heat or signs of recurring trouble.

Likely causes

  • Wiring chafe near door hinge, front fender, or rear lamp harness where movement fatigues insulation
  • Lamp socket corroded by moisture leading to short when vehicle vibrates or when wet
  • Stuck relay contacts in the hazard flasher causing constant high current draw
  • Incorrect bulb replacement (higher wattage halogen) or LED retrofit without proper resistors
  • Aftermarket trailer connector or accessory incorrectly wired to the hazard circuit
  • Short inside BCM or connector pin short at fuse/relay box (less common)

Fault status

⚠️ Status
Hazard lamp circuit overcurrent — fuse blows when hazard switch activated (possible short, faulty lamp/relay, or wiring fault).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

Similar codes

B1740 B1741 B1742 B1744 B1780
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Code

B1743

Other B — Body

Mirror Passenger Vertical Switch Circuit Short To Battery

Brand: Other
Type: B — Body
Views: UK: 21 EN: 36 RU: 22
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short to ground in the hazard/turn‑signal wiring (chafed or pinched harness)
  • Faulty hazard switch or flasher/hazard relay with internal short
  • One or more bulbs with internal short or incorrect (over‑wattage) bulbs installed
  • Corroded or water‑ingress damaged lamp sockets or connectors creating a short
  • Aftermarket accessories tied into the circuit incorrectly
  • Damaged fuse holder or poor contact causing arcing and repeated fuse failure

Symptoms

  • Fuse for hazard/indicator circuit blows immediately or shortly after hazards are switched on
  • No hazard or turn signal operation when fuse is blown
  • Fuse blows only when specific lamp(s) or trailer connector are connected
  • Visible arcing, melted fuse holder, burning smell near fuse box or lamp
  • Intermittent operation of indicators/hazard before fuse failure

What to check

  • Confirm correct fuse rating (do not replace with higher amperage fuse to 'fix' problem)
  • Visually inspect fuse and fuse holder for signs of melting, burning or poor contact
  • Inspect all lamp bulbs and sockets (front/rear/side) for corrosion, broken filaments or conductive debris
  • Disconnect hazard relay/ flasher module and check whether fuse still blows
  • Disconnect lamp connectors and trailer connector, then operate hazards to isolate the faulted section
  • Perform a wiring inspection along common chafe points (doors, fenders, rear quarter, trunk) looking for damaged insulation

Signal parameters

  • Typical bulb current: 21 W incandescent ≈ 1.7 A per lamp at 12 V (check vehicle-specific bulb wattage)
  • Hazard circuit total current (all bulbs active) commonly up to ~6–10 A for standard incandescent setups
  • Common fuse rating for hazard/turn circuits: typically 10 A–15 A (vehicle-specific — consult manual)
  • Fuse voltage at supply with ignition on and hazards activated: ~12 V (no more than ~0.5 V drop across good fuse/holder)
  • Ground resistance for lamp circuit: ideally

Diagnostic algorithm

  1. Do not replace fuse with a higher amperage. Replace blown fuse with correct rating to proceed.
  2. With ignition off, visually inspect fuse, fuse holder, and adjacent wiring for heat damage. Disconnect battery negative before major repairs.
  3. Remove all external loads: unplug front/rear lamp connectors and any trailer or accessory connections tied to the circuit.
  4. Replace fuse and activate hazards. If fuse does NOT blow, reconnect loads one at a time (or one lamp at a time) to identify which lamp/connector causes the fault.
  5. If fuse still blows with all lamps disconnected, pull the hazard/flasher relay and retest. If fuse no longer blows suspect relay/module or upstream short near fuse box.
  6. If a specific lamp causes the blow, inspect that lamp socket and wiring for corrosion, water, or pinched wires; repair or replace socket and harness as required.
  7. If fault is not isolated to a single lamp, systematically follow the harness from fuse box toward lamps, using an ohmmeter to check for unintended continuity to ground with the circuit disconnected (fused circuit = remove fuse first).
  8. Use an inline ammeter to confirm current draw when circuit is active; if high current persists with lamps disconnected, suspect short in harness or BCM and consider disconnecting BCM outputs for further isolation.
  9. Repair damaged wiring (replace sections or use proper splice/resealing techniques), replace faulty relay or sockets, and reassemble. Clear any BCM codes and retest.
  10. After repair, perform a final road/test check of hazard and turn signals and inspect fuse holder for heat or signs of recurring trouble.

Likely causes

  • Wiring chafe near door hinge, front fender, or rear lamp harness where movement fatigues insulation
  • Lamp socket corroded by moisture leading to short when vehicle vibrates or when wet
  • Stuck relay contacts in the hazard flasher causing constant high current draw
  • Incorrect bulb replacement (higher wattage halogen) or LED retrofit without proper resistors
  • Aftermarket trailer connector or accessory incorrectly wired to the hazard circuit
  • Short inside BCM or connector pin short at fuse/relay box (less common)

Fault status

⚠️ Status
Hazard lamp circuit overcurrent — fuse blows when hazard switch activated (possible short, faulty lamp/relay, or wiring fault).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

Similar codes

B1740 B1741 B1742 B1744 B1780
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