Auxiliary Heater - Description & Operation
The system consists of a fuel operated heater unit and a fuel dosing pump.
Fuel for the heater system is taken from the vehicle fuel tank, through a fuel line attached to the fuel pump module. Fuel is drawn from the fuel tank by the dosing pump to the heater unit. In the heater unit, the fuel delivered by the fuel pump is burned and the resultant heat output is used to heat the engine coolant.
An electronic control module integrated into the heater unit controls the operation of the heater unit and the dosing pump. The climate control unit controls the operation of the re-circulation flaps on initial start up.
Scheme 112
| Item Number | Description |
|---|---|
| 1 | Auxiliary heater bracket |
| 2 | Auxiliary heater assembly |
| 3 | Air intake hose |
| 4 | Air intake silencer |
| 5 | Exhaust silencer assembly |
| 6 | Coolant outlet hose |
| 7 | Coolant inlet hose |
| 8 | Fuel line |
The auxiliary heater is located behind the left hand side of the front bumper and is accessed via the radiator splash shield.
The auxiliary heater operates in two stages. The system will only ever operate if the engine is running. The ambient temperature has to be below 10° C (50° F) and the coolant temperature has to be lower than 87° C (189° F) at the start of the journey.
The first stage will operate until the coolant temperature reaches 87° C (189° F), and it will then go to the second stage until the coolant temperature reaches 90° C (194° F). At this point the system will switch off. It will switch on again if the coolant temperature drops below 79° C (174° F).
The auxiliary heater will not operate if
- the supply voltage is below 10.25V
- it is in 'fault lockout'
Principles of operation
The auxiliary heater is a fuel-fired unit which can only operate when the engine is running, when the ambient temperature is below 10 degrees C (50 degrees F), and the coolant temperature is below 87 degrees C (189 degrees F) at the start of the journey.
There are two stages to the operation of the system
Stage one (full power mode)
The system operates from cold until the coolant temperature reaches 87 degrees C (189 degrees F), when it switches to
Stage two (half power mode)
The system operates from 87 degrees C (189 degrees F) until the coolant temperature reaches 90 degrees C (194 degrees F), at which point the system switches off.
The system will switch back on if the coolant temperature drops below 79 degrees C (174 degrees F).
The auxiliary heater will not operate if
- The supply voltage is below 10.25 volts
- The system is in fault lock-out
- The fuel warning light is illuminated
- The coolant temperature is greater than 90 degrees
- The system does not receive a request from the climate control module
For additional information on the operation of the system. See Auxiliary Heater .