outdoor-sensor on a Danfoss heat pump: Sensor fault alternatively cable fault
Short answer
On a Danfoss heat pump, outdoor-sensor means: Sensor fault alternatively cable fault. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 2 sources
What it means
On the DHP-AQ
The manual says: Sensor fault alternatively cable fault.
Part involved: outdoor sensor.
Likely causes:
- Sensor or cable fault.
On the DHP-H
The manual says: Fault in outside sensor. When the control system calculates the heat demand, zero degrees is used.
Part involved: outdoor sensor.
Likely causes:
- Sensor fault or cable fault (cable often damaged by nails/clips per Danfoss troubleshooting guide).
Is it safe?
On the DHP-AQ
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Yes, when the condition clears (inferred).
On the DHP-H
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Yes, when the condition clears.
What you can check
On the DHP-AQ
- Note the exact alarm text. The manual allows acknowledging by setting operating mode OFF then back once; if the alarm returns, call an engineer.
On the DHP-H
- Note the exact alarm text. The manual allows acknowledging by setting the operating mode to OFF and then back to the previous mode - do this once; if the alarm returns, leave it and call an engineer. The heat pump keeps heating using 0°C as outdoor temperature, so comfort may be affected.
What the engineer will check
On the DHP-AQ
- Disconnect the sensor and measure resistance with and without its cable against the ohm table in 'Measurement points' (section 3.3); replace the sensor if out of tolerance, otherwise the cable.
Who to ask for: heat pump engineer.
On the DHP-H
- Disconnect sensor and measure resistance incl. cable, then sensor alone, against the 150 Ohm-type outdoor sensor table (e.g. 428 Ohm at 0°C); inspect cable route.
Who to ask for: heat pump engineer.
What you might notice
Sources
- Service Instructions DHP-AQ (VMGFJ202) ↗ · VMGFJ202 · page p.10; p.18 · Reviewed 23 September 2026
- Service instructions DHP-A, DHP-A Opti, DHP-AL, DHP-AL Opti, DHP-C, DHP-H, DHP-H Opti, DHP-H Opti Pro, DHP-L, DHP-L Opti, DHP-L Opti Pro (VMGFC302) ↗ · VMGFC302 (© 2010; PDF regenerated 2024-07-10 on assets.danfoss.com) · page printed p.35-36, p.42 (Table 16); PDF pp.37-38, 44 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026