Fiat 1998 Marea Weekend, Service Manual

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Marea-Marea Weekend®™ ®™
Auxiliary units
99 range
Climate control
50.
ADDITIONAL HEATER
The heating inside the vehicle by the heater unit is not sufficient when the engine is cold, especially for
diesel engines which take longer to reach their operating temperature. An additional heating system is
available on these versions which is activated when the engine is first running and is operational until it
reaches a certain temperature.
The system consists of an additional heating device, located on the coolant supply pipe from the engine to
the heater unit.
This device contains three heater plugs, very similar to those used for pre-heating the combustion cham-
bers.
Location of coolant heater plugs inside the vehicle
1. Additional heater
2. Heater plugs
3. Temperature sensor
The additional heater (1), which contains the three heater plugs (2), is located on the coolant supply pipe
to the heater unit.
The coolant temperature sensor (3) is fitted on the same pipe, immediately upstream towards the engine
thermostat.
The three relays are connected near the diesel filter, on a special bracket fastened to the engine compart-
ment bulkhead.
The system control unit is located under the dashboard, behind the glove compartment.
Operating logic
The operation of the heater plugs is controlled by an electronic control unit which operates either one,
two or all three of them providing a power output of 200W, 400W or 600W.
This control logic depends on:
- the temperature reached by the coolant as it leaves the engine;
- the level of power available;
- the engine rpm.
The first information is supplied by a special temperature sensor located on the supply pipe to the heater;
the control logic deactivates the heater plugs when the temperature of the coolant coming from the engine
exceeds 70°C.
The control unit also takes into account the parameter of the temperature of the air in the engine com-
partment: it is not meaured by a special sensor, but a theoretical value is taken equal to that of the coolant
when starting; the switching off value goes down to from 70°C to 65°C if the theoretical temperature of
the air is higher.
4F03DH01
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III-9&- Update
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