Duetto p4 space heater - problem

Hi to everyone ( and thanks for all you help, in advance),

My Carver p4, ignites, and blows cold air. But, when I press one of the heat settings it runs for a while (not producing any warm air) still blowing cold air, before shutting down.

The control unit flashes twice, which apparently could be a blocked flue or combustion motor failure.

Now, (excuse me if I'm being thick), but, there's the 2 inlet/outlet pipes inside the van, where the hot air is supposed to come out. But, are there any other inlets for any where else, that I should be checking?

Look underneath the drivers side sill towards the rear wheel and you will see two flexible pipes approx 1 1/2" diameter. The one nearest the front is the inlet pipe and the rearmost one the exhaust. If you can get an airline to them, give a good blast to clear any spiders webs or dust that may have accumulated inside. If the blower runs, give it time as it can take a good five minutes before you get warm air, providing it doesn't cut out again.