Malibu boiler not producing hot water: what's going on?

Malibu installs different hot water systems depending on the model and year of manufacture. The most common is the Truma Combi, a combination boiler that both heats and provides hot water on gas and/or 230V. In the higher segments you will often find an Alde system with a separate hot water boiler, and some older or more compact models have a separate Truma boiler (e.g. Truma Boiler 14 litre). Each system has its own typical faults.

Always start with the simplest checks, regardless of the system. Check whether the boiler is filled with water (air in the system can block the boiler), check the fuses in the 12V distribution board and check whether the 230V supply is working. For gas operation: is there enough gas and is the gas tap open? A common cause is an empty gas bottle or a faulty pressure regulator.

Diagnosis by power source

• Gas operation (Truma Combi or Alde): Can you hear the ignition clicking but the flame does not ignite? Then check the gas pressure (30 mbar) and the gas bottle. If the flame ignites but the water does not get hot, the heat exchanger may be scaled up or the circulation pump (on Alde) may be faulty.
• 230V electric: If the appliance does not work on 230V but does on gas, the heating element (spiral) is often faulty or the thermostat is broken. Measure the resistance of the element; if it is infinite, the element is burnt out. Also check the 230V fuse in the distribution board and the residual current device.
• 12V (only on Alde): The 12V option is only intended to keep the water warm while driving, not to quickly heat cold water. If the system does not work on 12V, check the fuse and the D+ (alternator) connection.

Another point to note is the safety valve (pressure relief valve). If it keeps dripping or leaking, the boiler may not build up enough pressure and therefore not work properly. A faulty temperature sensor or a stuck mixer tap can also give the impression that there is no hot water, even though the boiler is actually getting hot.

The cost of a repair varies widely. A new heating element for a Truma Combi costs roughly between 100 and 200 euros, excluding installation. A new circuit board can cost up to 400 to 600 euros. A complete replacement of a Truma Combi including installation is often between 2,500 and 3,500 euros. With an Alde system, parts are generally more expensive. Always have a diagnosis carried out by a certified motorhome technician before making large expenditures.

For more background on possible causes and solutions, see our general explanation about a boiler without hot water.