Ideal Logic System IE fault L4
Control/no flow thermistor fault
Gas boilerWhat it means
Fault detected with control or no-flow thermistor.
Likely causes
- Loose wiring connection to Flow Thermistor
- Faulty Flow Thermistor
- Loose wiring connection to PCB low voltage connector
- Faulty PCB
- Control thermistor fault
- No-flow thermistor fault
Where to start
- Is the wiring securely connected to the Flow Thermistor (located in the top of the Heat Exchanger)? If NO, securely connect the wiring to the Water Flow Thermistor.
- If YES, disconnect the wiring from the Flow Thermistor and check resistance using a suitable multimeter connected across the Thermistor's terminal pins.
- Is the Thermistor value correct? If NO, fit a new Thermistor.
The full answer, free
- 4 more checks in order
- The readings and component tests from the manual
- How to put it right, step by step
- The manual page for this fault (page 54), 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 System IE. Check the model on the data plate before you order parts.
Other Ideal Logic System IE fault codes
- F02Flame loss
- F04Flow thermistor fault
- F05Return thermistor fault
- F0DLow water flow / low water pressure
- F0UFlow/return differential greater than 50°C
- F10Spark generator fault
- F12Pump rotor blocked
- F13Pump fault
- F15Pump fault
- F16Gas valve fault
- F17Pump fault
- F2Flame loss
- F3Fan fault
- F4Control/no flow thermistor fault
- F5Return thermistor fault
- F6Outside sensor fault
- F8PCB unconfigured/faulty or gas valve short circuit
- F9PCB unconfigured/faulty or gas valve short circuit
- FDNo water flow
- FNFlame loss
- FUDifferential greater than 50°C
- L02Ignition lockout after 5 attempts
- L04Flow thermistor fault
- L05Return thermistor fault