Truma combi blown air heating

[JRD2026]

Evening everyone,
After a recent very cold trip to Wales, I decided that I better do some investigation into the blown air heating system in our 2005 Swift caravan.
While we were away, we need the heating on, but found the blown air to be blowing round cold air.
We used the electric space saver heating set to 2000 and the thermostat set to 9, heat came out from the fire nice and warm, but not the blown air.
With the caravan at home I took a look into what maybe happening.
The heat output from the elements heated up to 70 degrees, and the fan worked in manual and auto when switched on.
Next I took the fan housing off, the fan rotates, but found that it is in a housing.
So can't find anything wrong electronically or mechanical, so is the just a poor design? As cannot see how the hot air gets into the fan assembly effectively.
Any advice appreciated

 

[Mr Plodd]

Look underneath your caravan and see how many metres there are of totally uninsulated hot air ducting. You will probably then have a better understanding of the reason!

 

[IanB1485]

When you say 'cold air' did you actually measure its temperature at the outlets? . putting your hand if front of them can give misleading results, as you cant' detect 'hot' air at anything less than about 30 deg C due to water on the skin which evaporates actually cooling the skin. Secondly did you measure the current load on the mains with it set to 2kW ( should be about 8A) if only 4A then its only taking 1 kW and if 2A then 500W. Thirdly the fan is a forward curved centrifugal impeller as it spins it pushes air outward into its housing and through the supply tubes , drawing air in from its centre (third picture) and hence the rear of the top of the heater element /heat exchanger area.Fourthly did you check the impeller is firmly attached to the shaft and spins correctly and the faster you run the fan, the cooler the air will be . and Finally as Mr Plodd says if the supply tubes run unde the van at any point a lot of heat will be lost ( this usually happens at the rear of larger vans .You may also have a balancer lever which selects whether the rear of the van gets a larger or lesser portion of the air.From picture 2 you posted the fan housing may be fitted incorrectly the fan 'aperture' should line up with hole in the rear of the main unit.