Ideal Logic fault F5
Return thermistor fault
Gas boilerWhat it means
Return temperature sensor reading is out of range or disconnected
Likely causes
- Return thermistor resistance out of specification
- Return thermistor wiring disconnected
- Return thermistor wiring lacks continuity to PCB
- PCB fault
Where to start
- Remove return thermistor from CH return pipe
- Disconnect thermistor wires
- Measure resistance across thermistor terminal pins using multimeter
The full answer, free
- The readings and component tests from the manual
- How to put it right, step by step
- The manual page for this fault (page 49), right under the answer
Safety: Isolate gas and power before you open the case. If you have been into the gas side, do a tightness test, and a combustion and flue check before you hand back. Gas Safe (UK) or RGI (Ireland) work only.
From the Ideal manual for the Logic. Check the model on the data plate before you order parts.