A chap on Caravan Talk had his van to the Alde factory for the fluid changing.
Alde commented that the gas combustion fan was noisy ( no me neither ) to which he commented that they rarely used it on gas.
Alde's advice was that when you start the Alde up then to run it on gas for the first 15 mins or so then change to electric ( if on EHU of course ).
This reduces the chance of the gas jets and fan becoming blocked with debris,spiders webs for example.
I have heard much the same advice for the Dometic fridge.
As we haven't used the van for a while I think I will give the Alde and the fridge a short run on gas on my next visit to storage.