F80/F91 Fault — actoSTOR inlet sensor or pump issue

What does F80/F91 mean?

The boiler is faulting and showing F80 and F91, indicating a problem with the actoSTOR (shift load pump) inlet sensor or its associated wiring. This is often linked to the cylinder not charging.

• NTC defective
• NTC cable defective
• Defective plug connection on NTC
• Defective plug connection on the actoSTOR electronics
• Sensor plug has short to earth to the casing
• Short circuit in cable harness
• Sensor defective

Click steps to track your progress.

1. 1

   Inspect the NTC sensor and its cable for any damage or defects.

2. 2

   Check the plug connections on the NTC and the actoSTOR electronics for a secure fit.

3. 3

   Look for any signs of a short circuit in the cable harness or where the sensor plug meets the casing.

4. 4

   If issues persist, the NTC sensor itself may be defective and require replacement (contact a technician).