Temperature Control Internal

Temperature Control Internal
Temperature control
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Temperature control
Solar sensors
The solar sensor is installed in the indirect ventilation grille in the vicinity of the LED for the antitheft alarm
system to allow for varying light and heat source conditions (solar radiation) and to influence temperature,
air distribution and air volume control .
It consists of two photoresistors , one on left and one on right that sense the different intensity levels of
the solar radiation . The temperature control is influenced by the parameters stored in the EEPROM for
changing following functions:
The blower curve is shifted
The stratification air temperature is changed
The ventilation flap angles are changed
The sensor signal is output in a voltage range from 0 - 5 V and updated every 10 seconds . The signal
plausibility is checked by a limit monitoring facility so that the sensor influence may be disabled in the case
of fault .
Setpoint temperature value control
The temperature is selected separately for the driver and front passenger sides using the plus/minus
button . The setpoints are indicated in the LC display in 0.5 o C or 1 o F steps when the appropriate
plus/minus button is pressed. The displayed values correspond to a temperature which may deviate from
the setpoint values .
The temperature control function is deactivated when the setpoint temperature value on the driver's side is set
to minimum or maximum. Both water valves are closed in the minimum position and opened in the maximum
The defrost feature has a priority function in air distribution and in the control calculation for heating. The
defrost function is activated by means of the defrost stage (5th stage) in the blower switch.
At an outside temperature below 10 o C, the water valves are forced open.
If the outside temperature exceeds 10 o C, the setpoint temperature value for the driver's and passenger's
side is increased by 1 o C. At the same time, the heat exchanger setpoint value is increased by at least 30 o
Front mixing air control
A mixing air control function is used to control the outlet temperature at the ventilation nozzles in the case of a
reduction in the ventilation flap position or when the air conditioning system is switched on or off. The input
variables are the setpoint temperature value selected, the position of the mixing air flap control in the centre
grille and the temperatures of both ventilation sensors installed in the centre grille. The control then sets the
mixing air value to the value calculated from these variables, independently on the left and right.
Rear mixing air control
By means of a mixing air and shut-off flap installed in the unit, the air for rear air ventilation can be shut off or
its temperature infinitely controlled up to the heat exchanger temperature.
The position of the mixing air flap and thus the temperature of the outflowing air can be set electrically by
means of a mixing air control on the rear ventilation grille. The flap is also closed electrically by the rear
compartment switch on the rear grille.
Auxiliary water pump
An electrically operated auxiliary water pump is installed to ensure an adequate water flow at low engine
Temperature control
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speeds. This water pump ensures virtually constant engine speed-independent water flow through the heat
The auxiliary water pump is switched on at:
Engine temperature > 0 o C and heat demand on driver's side
defrost ON
maximum heating driver's side
residual heat function active
blower control wheel out of zero position
control unit OK
The auxiliary water pump is switched off at:
Engine temperature < 0 o C
no heating demand on driver's side
control unit defective
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