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Home / DTC / B1272 — Potentiometer of the ventilation servo motor - circuit failure

B1272 — Potentiometer of the ventilation servo motor - circuit failure

Detailed page for trouble code B1272.

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Code

B1272

LAND ROVER B — Body

Potentiometer of the ventilation servo motor - circuit failure

Brand: LAND ROVER
Type: B — Body
Views: UK: 6 EN: 14 RU: 9
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Page language: EN

Causes

  • Open circuit in potentiometer signal/return wiring
  • Short to ground or battery in potentiometer wiring
  • Corroded or loose connector at the ventilation servo
  • Failed potentiometer inside the ventilation servo assembly
  • Faulty climate control / body control module or poor module ground
  • Water ingress or mechanical damage to the servo/potentiometer

Symptoms

  • Inability to control vent/air distribution positions (e.g., stuck to dash/foot/defrost)
  • HVAC mode doors move to default/safe position or do not follow commands
  • Climate control displays incorrect vent position or shows error message
  • Noise from servo as it tries to move but position feedback incorrect
  • DTC B1272 stored in module, possibly with lamp or message

What to check

  • Read stored/active codes and freeze‑frame with a scan tool; confirm B1272 is current
  • Attempt to command the ventilation servo from a diagnostic tool and observe movement and feedback values
  • Visually inspect servo connector, pins and wiring for corrosion, chafing or damage
  • Wiggle the harness and connector while observing live feedback for intermittent behavior
  • Check for signs of water ingress in HVAC plenum or connector boot

Signal parameters

  • Reference supply (from module): about 5 V (Key ON) to potentiometer reference pin
  • Signal voltage: varies approximately 0–5 V proportional with vent/damper position
  • Signal behavior: smooth change without jumps or dropouts when commanding servo
  • Resistance across potentiometer typically in the low kΩ range (varies by design); should change smoothly across travel

Diagnostic algorithm

  1. Connect a compatible scan tool. Record codes, freeze frame, and live data for ventilation servo position/pot signal. Note command vs feedback values.
  2. With key ON (engine off), command the servo through its full travel via diagnostics while watching live signal. Observe whether feedback voltage changes smoothly from ~0–5 V.
  3. Inspect the servo connector and wiring harness visually. Check for corrosion, bent pins, broken wires, moisture, or rodent damage. Repair as needed.
  4. Perform wiggle test on harness and connector while monitoring live signal for intermittent faults. Move related body panels to replicate environment.
  5. Backprobe connector at the servo: verify 5 V reference present, solid ground, and that signal voltage changes as servo moves. No reference or ground fault indicates wiring/module issue.
  6. If reference and ground are present but signal is fixed, measure potentiometer resistance across terminals while operating servo (if accessible). Look for open or inconsistent resistance change.
  7. If wiring and connector test good but signal remains invalid, replace the ventilation/air‑door servo assembly (contains potentiometer) and retest.
  8. If replacement does not clear the fault, test/inspect the climate control/body control module power, grounds, and connectors; consider module fault and consult manufacturer procedures.
  9. After repair, clear codes, cycle ignition, and verify correct operation through full diagnostic actuation and normal vehicle operation.

Likely causes

  • Damaged harness or pin pushed out at servo connector
  • Corrosion/water in HVAC case or connector causing intermittent contact
  • Failed integrated potentiometer in the vent/air‑door servo
  • Connector pins shorted by debris or rodent damage
  • Blown 5V reference or poor ground at control module

Fault status

⚠️ Status
Potentiometer circuit failure detected for ventilation servo motor. Signal missing, out of range, shorted or intermittent; causes loss of valid position feedback for HVAC air‑distribution control.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

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