Fault codes / Truma AquaGo / 4
Truma AquaGo code 4
What it means: Water over 185 F (WOS).
What to check
Too little flow, scale, bad temperature sensor, or hot water entering the unit.
Learn the system
Practice it on a service call
Guided diagnosis
Other Truma AquaGo codes
- Truma AquaGo code 1 No flame after 3 tries
- Truma AquaGo code 2 Overtemperature switch (EOS or BOS) open
- Truma AquaGo code 3 Exhaust pressure switch
- Truma AquaGo code 5 Flame seen at the wrong time
- Truma AquaGo code 6 Safety circuit switch open
- Truma AquaGo code 7 Control board memory fault
- Truma AquaGo code 9 Outlet sensor (WOT) fault
- Truma AquaGo codes 10 and 11 Safety circuit or watchdog fault
- Truma AquaGo codes 12 and 16 Internal control fault
- Truma AquaGo code 13 Shut-off valve current over 1000 mA (short)
- Truma AquaGo code 20 Inlet sensor (WIT) fault, or inlet below 14 F
- Truma AquaGo code 21 Circulation sensor (WCT) fault
- Truma AquaGo code 22 Gas valve modulator fault
- Truma AquaGo code 23 Voltage over 16.4 V
- Truma AquaGo code 24 Voltage under 10 V
- Truma AquaGo code 25 Flue fan current fault
- Truma AquaGo code 26 Circulation pump current fault
- Truma AquaGo code 27 Pump running dry
- Truma AquaGo code 28 Low gas pressure
- Truma AquaGo code 29 Too much hot water demand
- Truma AquaGo code 30 Freeze risk below about 27 F
- Truma AquaGo code 31 Decalcification finished
- Truma AquaGo codes 32 and 33 Antifreeze kit current fault
Full field guide: Truma AquaGo tankless water heater
Codes come from the maker manuals and public service sheets. Your model's own chart always wins, and LP and 120 volt work belongs to a qualified technician.