Truma AquaGo tankless water heater fault codes
Truma AquaGo tankless, about 60,000 BTU. It has a built-in decalcification (descale) routine for routine maintenance. Gas heat, 12V control.
Truma AquaGo code 1
No flame after 3 tries. Propane valve open, tank has gas, regulator, bleed air from the gas line, igniter and electrode condition.
Truma AquaGo code 2
Overtemperature switch (EOS or BOS) open. Let it cool, check water flow and scale, then test the switch. Find why it overheated.
Truma AquaGo code 3
Exhaust pressure switch. Exhaust or intake blocked, hose, switch. Clear the vent, then test the switch.
Truma AquaGo code 4
Water over 185 F (WOS). Too little flow, scale, bad temperature sensor, or hot water entering the unit.
Truma AquaGo code 5
Flame seen at the wrong time. Gas valve leaking by or a faulty flame sensor. Service the valve.
Truma AquaGo code 6
Safety circuit switch open. Check the switches and wiring in the safety loop. Reseat plugs.
Truma AquaGo code 7
Control board memory fault. Reset power. If it returns, replace the control board.
Truma AquaGo code 9
Outlet sensor (WOT) fault. Reseat and measure the outlet sensor. Replace if open or shorted.
Truma AquaGo codes 10 and 11
Safety circuit or watchdog fault. Cycle power. If repeated, control board.
Truma AquaGo codes 12 and 16
Internal control fault. Cycle power. If repeated, control board.
Truma AquaGo code 13
Shut-off valve current over 1000 mA (short). Check the valve and its wiring for a short. Replace the valve if shorted.
Truma AquaGo code 20
Inlet sensor (WIT) fault, or inlet below 14 F. Reseat and measure the sensor. Check that it is not freezing.
Truma AquaGo code 21
Circulation sensor (WCT) fault. Reseat and measure the sensor.
Truma AquaGo code 22
Gas valve modulator fault. Check the plug and coil. Replace the gas valve if the coil is open.
Truma AquaGo code 23
Voltage over 16.4 V. Check the charger or converter output. Measure at the heater.
Truma AquaGo code 24
Voltage under 10 V. Low battery or voltage drop. Measure at the heater while it runs.
Truma AquaGo code 25
Flue fan current fault. Fan blocked, bad fan, or wiring. Check for debris.
Truma AquaGo code 26
Circulation pump current fault. Pump jammed or wiring. Check for debris or scale.
Truma AquaGo code 27
Pump running dry. Air in the lines. Open each hot faucet and bleed all the air out.
Truma AquaGo code 28
Low gas pressure. Tank low or regulator weak. Read pressure under load.
Truma AquaGo code 29
Too much hot water demand. Too many taps at once for this unit. Reduce flow.
Truma AquaGo code 30
Freeze risk below about 27 F. Drain the unit, or keep it on eco or comfort mode so it can protect itself.
Truma AquaGo code 31
Decalcification finished. Normal message. Finish the descale routine.
Truma AquaGo codes 32 and 33
Antifreeze kit current fault. Check the antifreeze kit wiring and valve.
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Guided diagnosis
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.