My 1990 camper has one of the factory rear heaters (coolant fed) which is under my R&R bed now . When i fitted the bed I didn't think the heater worked so I didn't leave a vent for it . However whilst on holiday my 3 yr old son turned the switch on(next to heater controls) and low and behold after three miles smoke was coming out from under the seat as dust started to burn on the elements .Fortunately no harm done. my question is should this heater have a fan blower to move the warm air out or what I assumed that because i couldn't hear a blower working that the heater was duff(clearly not) Does anyone have any experience how these heaters work ...Thanks Mark
mines a coolant fed heater in the rear as well its got a valve on it that i presume should have a cable connected to it running to the front so i can control the amount of hot water flowing through it. but i havent and there's also a fan speed switch next to the heater controls that makes the fan in it go
Mine has the same operating cable connector and is also without said cable.
I think the cable was not fitted and the heater blower was the only control.
I've got one sat in a box waiting to be fittted, the heat only comes from the coolant and the lever is a simple on/off affair basically in the winter you turn it on, then off in the summer. There should be a second 3 position fan switch on the dash next to the main heater controls. When off no air passes over the heater matrix so even if it's turned on it won't heat the van. If you've had smoke from under there I'd check the fan is actually turning when on, I've not heard of it but I suppose the blower could seize like the front ones do. There is also a resister pack on the end of the motor to control the speed, this will get hot so dust could be burning off there, or the smoke was from the bit of wood blocking the vents, by all accounts they are very efficient when on full speed.
If the fan works on all speeds either cut a hole in the bed base to make use of the heater or unplug the wiring loom either at the switch or fan so it can't be turned on again - if you decide not to use it think about taking it out, they take up quite a bit of space under the seat. They are easy enough to remove you just need to take out the T connectors in the main heater pipes and replace with a straight connector from B&Q. Heater with switch goes for about £40 through the classifieds if you then wanted to sell it.
The rear heater feeds from the same water cuircuit as the front one.
On the side of the rear heater there is this valve (unlabelled) that is a on-off valve (Winter/Summer setting) that either allows coolant to pass through the heater or not.
Once that valve is open, when you put on the cab heater (and therefore allow coolant to circulate) the rear heater also gets hot (very hot actually).
The front heater control to some degree also controls how hot the rear one gets by regulating the amount of coolant that circulates through the whole system.
The blower is just that ...a fan motor that blows air through the rear heater matrix. That also works when the heater is off, blowing cold instead of hot.
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The rear heater matrix and all its valvery is also quite prone to leaks ...not the most sturdy of components.
.Fortunately no harm done. my question is should this heater have a fan blower to move the warm air out or what 
I assumed that because i couldn't hear a blower working that the heater was duff(clearly not) Does anyone have any experience how these heaters work ...Thanks Mark 
