Can anyone explain the interconnection of the engine coolant powered Auxilary Heater that is installed under the driver seat? When the heater is switched on the fan runs but there is no heat, the pipes under the seat not getting warm. Are these pipes T'd into the cab heating pipework with a solenoid to allow flow to the auxillary heater when it is switched on?

On older fiat based motorhomes I believe it had a valve on the door pillar somewhere not sure if this applies to you