Matthew Birks, technical expert from Eberspächer, advises on maintaining your on board diesel fuelled air heating system.

If your boat is a working boat or you live aboard we recommend having an accredited dealer inspect your installation and service your heater every one to two years.

If you are an occasional boater, though, the recommendation is having an accredited dealer inspect your installation and service your heater every three to four years. However, poor fuel condition, high sulphur gas oil or operating the heater as a ‘frost watch heater’ will shorten service intervals.

You may also be able to tell if the heater requires a service if you may notice the heater’s exhaust start to produce grey smoke or white diesel vapour while the heater is trying to start or the heater takes two or three attempts to start.

Getting a heater serviced

To get the heater serviced, contact your local accredited dealer who will remove and refit your heater or, alternatively, remove the heater yourself and send it to an accredited dealer who will service and return it back to you.

Bear in mind that if you remove the heater, the dealer will also require the fuel metering pump (if separate from the heater). If there are any installation safety issues that are affecting the heater mechanically, these may not be spotted if you remove/refit the heater yourself.

Use of Paraffin

In terms of running a heater on Paraffin to de-coke it, if your heater has had a short term problem (blocked exhaust or combustion air pipe etc…) and has an oily soft carbon build up, then Paraffin may help.

If your heater has had a long term problem and the carbon has built up and been baked on over a long period of time, then paraffin will not help. Warning – never use petrol or any type of petrol mix.

Why has my fore cabin become cold or slow to warm up?

This is normally due to poor or incorrect duct balance. Example: If you have a large duct pipe to the aft cabin and a small outlet in the forward cabin, then a large majority of the air will escape into the aft cabin. Restricting the air flow in the aft cabin and ensuring smooth and unrestricted air flow to the forward cabin will improve temperature and air volume. Fitting wider ducting in the forward cabin should be done if at all possible.


Eberspächer have recently introduced their next generation of air heaters in the 2kw and 4kw ranges covering most power and sail boats up to 40’, featuring a brushless motor, near silent fuel pump and CAN interface. With this new technology, service intervals have been extended and the internal workings less exposed to faults in a harsh environment. /


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