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