Heater Not Working — Diagnosis Guide

What This Is

Most motorhomes use a Truma or Alde heating system. When the heater fails to start or shuts down unexpectedly, the cause is usually one of a handful of common issues. This guide walks through them in order.

Tools & Parts Required

Step-by-Step Instructions

1. 1

   Check the gas supply first. Is the gas bottle open and does it have gas in it? Try lighting the hob — if the hob lights, gas is reaching the vehicle.

2. 2

   Check the battery voltage. Most Truma and Alde systems require at least 11.5V to operate. A low battery will prevent ignition. Check the leisure battery voltage with a multimeter.

3. 3

   Check the heater's control panel for error codes. Truma systems display fault codes (e.g., E1, E2) that indicate the specific problem. Refer to your Truma manual for code definitions.

4. 4

   Check the flue outlet outside the vehicle. The flue must be clear of obstructions — leaves, mud, or insect nests can block the flue and cause the heater to shut down on safety lockout.

5. 5

   Check the air intake and combustion air supply. On Truma Combi units, there are two external vents — one for combustion air in, one for flue gas out. Both must be clear.

6. 6

   Reset the heater. Switch it off at the control panel, wait 60 seconds, and switch it back on. Many lockout conditions reset automatically after a brief pause.

7. 7

   If the heater attempts to light but fails after 3 attempts, the igniter or thermocouple may be faulty. This requires a service engineer.

8. 8

   For Alde wet central heating systems, check the system pressure gauge. It should read between 1.0 and 1.5 bar when cold. Low pressure indicates a leak or the need to top up the system.

Common Mistakes to Avoid

Safety Warnings

When to Call a Professional