Bongo Fury

Hi everyone,
Billie bongo 2.5 diesel WLT 1998 has the digital air conditioning system with front and rear cooling / heating. The issue is that it is not 'heating'. After recent refridgerant hose change and re-gassing, it cools the cab very nicely but wont heat.

What I have done so far:

• I have checked that the 'air flaps' of the ventilation box located between passenger and drivers legs . The flap on passenger side operates as I dial the required temperature up and down. The one on the drivers side works when windscreen is selected on the AC control.
  As I dial the required temperature down to below ambient temperature, the passenger side flap rotates anti-clockwise and the air coming out starts to cool as expected.
  As I dial the required temperature up to its max of 32 degrees, the passenger side flap rotates clockwise and the fan speed increases but the air now being delivered is only luke warm at best.

Other observations:

• Starting the engine cold and running on tickover it takes about 13 minutes for the temperature guage to get to normal level (11 oclock).
  The large fan behind the radiator has not yet switched on and engine seam to be cooling adequately.
  If I turn on Auto on the AC system and require temp set to max. The large fan behind the radiator switches on and runs continuously.
  If I dial down the temperature to 18 the same fan cycles on and off at about 15 second intervals.
  Fluid in the engine cooling system is at the correct level and always has been over the last couple of years.

So my questions are:
Why is the air not being heated properly?
Where does the heat for the ventilation system come from. Does it come from the engine cooling system?
Any ideas of what I should check next?

The heat comes from the engine coolant always flowing thru the heating matrices, so your engine has to be running and hot, but then heat should be instant, otherwise its suggests that the heating matrix at the front is blocked and possibly the rear as well if that doesn't give out heat either.
This normally requires a flush of the coolant system and then specifically flushing the matrices to get them really clear, then re-filling coolant and bleeding the engine to get rid of trapped air.

OK thanks Geoff,
Where are the 'heating matrixes' located? How do I get to them?

The front one is accessed from the passenger side footwell and slides out from the central air box into the footwell see here www.g8dhe.net/bongo_images/Paul_Horsfal ... placement/
Oh be warned the plastic after 20+ years will be brittle treat GENTLY!!!!