Hot water issue

sounds like the system would be similar to what we had on the Bolero (and on our current van) in that it is a pressure based system where the water pump will run if the pressure in the pipe is low...tap open...and stop when pressure is high....tap closed....

this indicates that you have some sort of blockage in the hot system...

i assume all hot taps (sink, washroom, shower) are affected in the same way?

if so, the blockage is at or close to the tank.

perhaps the draining down caused an issue of some sort...

i would go through the draining process again and refill the hot tank from scratch, and try again.....

sorry, can thelp more than this...

Is the hot tank drain open?

Has the dump valve activated on the Truma heater?

Assuming that the manual drain valve has been closed it sounds like an air block. I often find that it takes far longer  for the hot side to get up and working compared to the cold. I would go along with BB's suggestion of dumping the water out of the system by using the manual flip drain valve and refilling the system but wait until the pump stops before operating the taps. You may well still get a lot of hissing and spitting from the hot tap until you get the air out of the system. Alternate between hot and cold and hopefully the hot side should start working normally. In such circumstances, once the problem seems to be corrected that the water can take a long time to heat up on electrics as a secondary issue. If that happens try it on gas and you should be OK.

David

If there were an air lock or the hot water tank were drained, the water pump would still run as it does when draining.

the only time the pump stops is when the system is fully pressurised, hence my suspicion of a blockage 

Thanks all for your advice/information. Have tried a number of ways to get the water through but no luck. Have a few things left to try though.  

are all the hot taps 'blocked' or just one (or two)?

It would also be interesting to know whether you can hear air escaping from the taps, like a hissing sound?

David

agree with David, when venting the system after a draindown, you will/should be getting lots of spluttering.

also, did you hear the hot water boiler filling as you put water in... with the pump on, this is the first thing that will happen as cold water from the fresh tank is drawn into the combi boiler.

Check that the non return valve in the supply from pump to water heater is not stuck closed. also some vans have an isolator valve in the hot water supply so that you can use the cold water system without filling the boiler, check this is not closed if fitted.