Code
B1289
ALFA ROMEO
B — Body
Right air intake potentiometer servo open circuit
Views:
UK: 8
EN: 19
RU: 9
AI status
Completed
Completed
100%
Causes
- Open or broken signal wire between potentiometer/servo and control module
- Corroded, loose, or damaged connector at the actuator or module
- Failed potentiometer inside the servo (internal open)
- Moisture or contamination causing intermittent/open circuit
- Faulty ground or supply to the actuator/potentiometer
- Control module input circuit fault (rare)
Symptoms
- HVAC right air intake door stuck or not responding
- Incorrect airflow distribution from right side vents
- HVAC runs in default or limp mode
- DTC stored (B1289) and possibly related HVAC codes
- Intermittent operation of right intake door/servo
What to check
- Verify the DTC with a scan tool and record freeze frame/live data for the right intake potentiometer
- Visually inspect the right intake actuator, connector and wiring for damage, corrosion, or pins pushed out
- With ignition ON, wiggle the harness and connector while watching live potentiometer signal for intermittent changes
- Measure supply voltage at the actuator connector (usually +5V reference) and check for a good ground
- Measure the potentiometer signal voltage while operating the HVAC controls across full travel — expect a variable voltage change; open circuit will show no signal or OL
- Check continuity between actuator connector and control module pins for open circuit
Signal parameters
- Reference supply: typically +5 V (ignition ON) to potentiometer Vref pin
- Signal voltage (position): varies approx. 0.5–4.5 V depending on door position (should change smoothly as door moves)
- Open-circuit indication: infinite resistance or OL on resistance check; no signal voltage present
- Potentiometer resistance (typical range): ~2 kΩ–20 kΩ (manufacturer dependent)
Diagnostic algorithm
- Retrieve B1289 and any related HVAC DTCs with a scan tool and note live data for the right intake potentiometer
- Perform a visual inspection of right intake actuator, connector and wiring for damage or corrosion
- With ignition ON, backprobe the connector at the actuator: verify Vref (≈5 V), signal voltage, and ground presence
- Operate the HVAC controls to command the door while observing the signal voltage — confirm it varies smoothly; if no variation, proceed
- If signal is absent, disconnect actuator and measure resistance across potentiometer pins; open (OL) indicates internal failure
- Check continuity of signal and ground wires from actuator connector to control module connector — repair any opens or high-resistance connections
- If wiring and connector are good but potentiometer shows open, replace the right intake actuator/servo
- After repair, clear codes and verify proper operation and that the signal voltage varies across full travel
- If problem persists and wiring is confirmed good, test or replace the HVAC control module as a last resort
Likely causes
- Broken harness between right intake actuator and HVAC control module
- Connector pins pushed out, bent or corroded at actuator
- Internal potentiometer element failure inside right intake servo
- Water ingress into the actuator connector or casing
- Poor ground at chassis or module mounting
Fault status
Status
Right air intake potentiometer servo — open circuit detected. No valid position signal from the right air intake actuator. Inspect actuator, connector and wiring; replace actuator if internal potentiometer is open.
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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