Failure-Short-circuit-on-sensor on a Worcester Bosch heat pump: Alarm window: Failure / Short circuit on sensor
Short answer
On a Worcester Bosch heat pump, Failure-Short-circuit-on-sensor means: Alarm window: Failure / Short circuit on sensor. The heat pump stops until the fault clears or is reset. 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 Greensource air to water heat pump (monobloc with HWDU)
The manual says: Alarm window: Failure / Short circuit on sensor.
Part involved: temperature sensors (e.g. T3 hot water).
When it shows: Temporary fault; defective sensor or incorrect connection.
Likely causes:
- Temporary fault; defective sensor or incorrect connection.
On the Greensource Split HP Hydrolight / Hydrocomfort
The manual says: Alarm: Failure / Short circuit on sensor.
Part involved: temperature sensors.
When it shows: Occasional fault; sensor fault or incorrect connection.
Likely causes:
- Occasional fault; sensor fault or incorrect connection.
Is it safe?
On the Greensource air to water heat pump (monobloc with HWDU)
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Select Acknowledge on the control panel (manual says there is never a risk in resetting an alarm); heat pump restarts within ~15 min if there is demand. Call the installer if the alarm recurs.
On the Greensource Split HP Hydrolight / Hydrocomfort
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Acknowledge by pressing the rotary selector (Acknowledge) on the Hydrolight/Hydrocomfort user interface.
What you can check
On the Greensource air to water heat pump (monobloc with HWDU)
- Read and note the full alarm text shown on the controller and pass it to your installer.
- Select Acknowledge on the control panel (manual says there is never a risk in resetting an alarm); heat pump restarts within ~15 min if there is demand. Call the installer if the alarm recurs.
On the Greensource Split HP Hydrolight / Hydrocomfort
- Read and note the full alarm text shown on the controller and pass it to your installer.
- Acknowledge the alarm once on the control panel; if it returns, call the installer.
What the engineer will check
On the Greensource air to water heat pump (monobloc with HWDU)
- Check sensor connection and resistance (chapter 15.4).
Who to ask for: heat pump installer / electrician.
Certification: Electrical work to BS 7671 by competent person.
On the Greensource Split HP Hydrolight / Hydrocomfort
- Check sensor connection and sensor (chapter 11.4.5).
Who to ask for: heat pump installer / electrician.
Certification: Electrical work to BS 7671 by competent person.
What you might notice
Sources
- Installation Manual Air to Water Heat Pump with DHW distribution unit Greensource 6/7/9.5 kW ↗ · 6 720 641 467 (2010/01) · page 41-42 · Reviewed 23 September 2026
- Installation, Commissioning and Servicing Instructions Greensource Hydrolight and Hydrocomfort (ODU 7.5-12) ↗ · 6 720 806 629 (2013/02) · page 64 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026