What it means
Vaillant's English fault table abbreviates this as 'Sensor fault: Capac. outlet temp.'. The same manual mentions a 'condenser outlet temperature sensor (subcooling)' in another fault's remedy, which appears to be this sensor. F.825 is the matching fault for the inlet sensor.
What to check, in order
- Reset once
Press the reset button on the control module. If the fault comes back after several resets, Vaillant says to contact Customer Service.
- Leave the casing closed
The sensor is inside the outdoor unit, so this is a job for an engineer.
When to call your installer
Call your installer. Vaillant's remedy is to check the sensor and replace it if necessary, and to replace the wiring harness if needed.
A repair visit will usually check the sensor's reading and its wiring.
- Note the model and serial number. They're on a label on the rating plate on the outdoor unit, and on the indoor unit or cylinder.
- Write down the exact code, and what the appliance was doing when it appeared.
- Check whether it's still under warranty. If it is, the repair may cost you nothing.
Quick answers
What does the Vaillant aroTHERM F585 error code mean?
The heat pump is not getting a usable reading from one of the temperature sensors in its refrigerant circuit, most likely the one at the condenser outlet. Vaillant says the sensor is either not connected or its input has short-circuited. Vaillant's English fault table abbreviates this as 'Sensor fault: Capac. outlet temp.'. The same manual mentions a 'condenser outlet temperature sensor (subcooling)' in another fault's remedy, which appears to be this sensor. F.825 is the matching fault for the inlet sensor.
Can I fix Vaillant aroTHERM F585 myself?
Engineer only (engineer visit). Start with: reset once; leave the casing closed. Call your installer. Vaillant's remedy is to check the sensor and replace it if necessary, and to replace the wiring harness if needed.
Is Vaillant aroTHERM F585 worth repairing?
Worth fixing. Vaillant's listed causes are the sensor and its wiring, so this is normally a routine repair.
Checked against
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.