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Premium Member
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Additional heater is most likely a remotely mounted diesel burner designed to speed warm up in colder climates.
It's actually an electrical resistance heating element ....

from (comparable) 147 diesel :

The climate control via the heater unit is insufficient when the engine is cold, especially in Diesel engines which are slow to warm up.

These engines may optionally be fitted with a supplementary heater system. This remains active from the moment when the engine is turned on until a certain temperature is reached.

The system consists of an additional heater, located in the heater unit: the device contains three resistances (PTC).

The operation of the resistances is controlled by the climate control unit which either operates only one, two or three of them, providing gradual heating, with a maximum power of 700 W following a logic which depends on:

the temperature of the engine coolant (about 60° ?);
the engine speed (which should be above 700 rpm).
the battery voltage (which should not go below 12.2 V).
For more details Characteristic of working principle 5040 AIR CONDITIONING CASING AND COMPONENTS .

The device is controlled by means of two relays; one is located in the engine compartment control unit, the other on the actual heater unit. The supply line is protected by a specific maxifuse, again in the engine bay control unit.

3,201 Posts
So it’s basically an element in the heater box then that just warms the air rather than coolant like aux heaters and the ford type with 3 glow plugs in.
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