Truma Water Heater Flashing Light: AquaGo Codes
On this page (6 sections)
The Short Answer: On a Truma AquaGo, a yellow LED that flashes twice, pauses, and repeats means the heater has stored a fault. The code itself is shown by a red LED under the switch behind the exterior access panel, as eight short and long blinks repeating every three seconds. Write the pattern down, reset once, and call a Truma service center if it comes back.
Two lights, two jobs
- Yellow LED on the interior control: steady during normal operation. A repeating double flash means “a fault has occurred.” It does not identify the fault.
- Red LED at the heater: behind the exterior access panel, under the rocker switch. It flashes the actual code. Short blinks count as 0 and long blinks as 1, so each code is an eight-place pattern.
- CP plus digital control: coaches with a CP plus panel show the same faults as letters and numbers on screen (for example W 31) instead of blink patterns.
Common AquaGo codes
These meanings come from Appendix A of the AquaGo operating instructions (PDF (opens in a new tab)) and Truma’s error code tech tip (opens in a new tab). The appendix lists more internal faults than shown here. They apply to the AquaGo only, not to Truma Combi heaters or Alde boilers.
| Code | Red LED (s = short, l = long) | Meaning | What to do |
|---|---|---|---|
| 1 | s,s,s,s,s,s,s,l | Flame not detected after three ignition attempts | Check that LP is on and other LP appliances light; reset once |
| 2 | s,s,s,s,s,s,l,s | Exhaust or burner over-temperature switch open | Do not keep resetting; service |
| 3 | s,s,s,s,s,s,l,l | Exhaust pressure switch fault, for example a blocked exhaust channel | Look for an obvious external blockage at the vent; service if it repeats |
| 4 | s,s,s,s,s,l,s,s | Water over-temperature switch opened (above 185°F) | Service |
| 23 | s,s,s,l,s,l,l,l | Supply voltage too high (above 16.4 V) | Have the converter or charging system checked |
| 24 | s,s,s,l,l,s,s,s | Supply voltage too low (below 10 V) | Charge the battery or reduce the 12-volt load |
| 27 | s,s,s,l,l,s,l,l | Circulation pump running dry | Fill the water system and run the faucets to clear air |
| 28 | s,s,s,l,l,l,s,s | Gas pressure too low | Check the cylinder level and valve |
| 29 | s,s,s,l,l,l,s,l | More hot water demanded than the heater can supply | Reduce flow or the number of open taps |
| 30 | s,s,s,l,l,l,l,s | Risk of freezing | Drain the heater, or run it in Eco or Comfort mode |
| 31 | s,s,s,l,l,l,l,l | Decalcification finished | Return the control to Eco or Comfort |
Resetting it once
Truma’s procedure is to switch the appliance off, wait five seconds, and switch it back on. If a code is still displayed, the instructions say to contact an authorized Truma service center. This matters most for codes 1 through 4. A heater that fails to light three times, or opens an over-temperature or exhaust switch, has a combustion or gas problem that more restarts will not solve.
If you smell LP, do not reset at all. Close the cylinder valve, get everyone out of the coach, and call for help from a safe distance.
Codes that are not really failures
Code 31 is a reminder that the descaling cycle has ended. Codes 29 and 30 are warnings about how the heater is being used or stored. Code 27 often appears after the water system was drained or winterized and has not been fully refilled. These usually clear once the condition is fixed.
What the service center checks
For flame, switch, and exhaust codes, the technician looks at LP supply pressure, the flue fan and exhaust path, ignition and flame detection, and the safety switches inside the sealed combustion section. Owners should not open that section or bypass a switch.
Frequently Asked Questions
Q: My Truma isn’t an AquaGo. Does this table apply? A: No. Truma Combi heaters use the CP plus display and have their own code list in the Combi manual. Alde systems are covered in Alde water heater not working. Suburban and Atwood tank heaters have a single fault lamp; see RV water heater fault light.
Q: I can only see the yellow light blinking. Where is the red one? A: It is on the heater itself, under the rocker switch behind the exterior access panel. The yellow double flash only tells you to go and read it.
Q: The heater shows no code but the water is still cold. What next? A: Check bypass valves, flow, and LP supply as described in Truma AquaGo problems.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- Truma AquaGo operating instructions, Appendix A: error codes (opens in a new tab)Truma AquaGo RV water heaters; red LED flash codes 1 through 33.
- Truma: tech tip, AquaGo error codes (opens in a new tab)Truma AquaGo with analog panel or CP plus control.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
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