Aqua-Hot AHE-250-D03 error code D1 LED OFF
D1 is the Heating Status light (orange) on the relay control board - it illuminates ONLY when the burner and/or electric-element switch is on AND the control thermostat is calling for heat. A dark D1 with no active heat call is NORMAL, not a board fault.
What to check, and in what order, is in the app. The flow Aqua-Hot Reporter — Fault Screen Triage walks this code step by step with the pass/fail measurements, wiring schematics and procedures that go with it, and it works offline in the bay.
Start free trial 14 days free, no card neededDocumented in
- Aqua-Hot 200-Series 250P/250D Service ManualAqua-Hot
- Aqua-Hot Heating Systems Service Manuals — aquahot.com
- Aqua-Hot Tech Support 800-685-4298 (Fort Lupton, CO)
- AquaHot 250 D03 Diesel Hydronic Technician Service Diagnostic Reference (rv-tech-resources/53-aquahot-250-hydronic/AquaHot_250_D03_Diesel_Hydronic_Technician_Service_Diagnostic_Reference.md)
Related codes
- BURNER FAILED TO IGNITEDiesel burner attempted ignition but the photo-eye did not detect a…
- OVERHEAT TRIPBoiler-coolant high-limit switch (215 deg F trip) opened, disabling…
- D4 LED NEVER ILLUMINATESOn the AHE-250 relay control board the indicator LEDs are D1 Heating…
- D5 LED OFF (OVERHEAT INDICATION)On the AHE-250 relay control board D5 = Burner Status (green) -- it…
- COOLANT LEAK UNDER UNITPink/red boiler antifreeze visible below the Aqua-Hot cabinet. Loss…
- SMOKE OR SOOT AT EXHAUSTVisible black smoke or accumulating soot at the exhaust pipe…