Left vent temperature sender -G150
Location, Fig.: N87-0786
A Connector of
temperature sensor -G150
1 Left vent
temperature sender -G150
The air conditioner is
regulated within an overall temperature range between 18°C and 28°C. However,
the possibilities of individual climate settings for each selectable position
must be set against the fact that the climate zones are not physically separated
from each other.
In the selected
automatic function the air conditioner uses the sensors to determine how much
the air for the climate zone concerned needs to be heated or cooled in order to
deliver the selected temperature.
In this, the air
conditioner control unit determines the flow rate of the engine coolant in the
heating circuit through the heat exchangers or the cooling power of the
refrigerant circuit, as appropriate. The air conditioner control unit decides
according to the requirement, for example that the regulated warm or cooled air
for ventilation is routed to the "driver" and "front
passenger" climate zone and, with the (optional) 4-zone air conditioner,
to the left and right rear passengers.
The design layout with
two adjacent heat exchangers provides a right/left split of the passenger
The temperature of these
two air flows for the left and right halves of the vehicle is primarily
determined by the temperature setting at the front seat positions.
The left vent temperature
sender -G150 is located in the heater/air conditioner unit above the left side
air vent duct to the left footwell.
The air flowing out of
the heater/air conditioner unit into the passenger compartment is recorded with
a temperature-sensitive resistor and so is available as an influencing variable
in the temperature monitoring and control function of the operating and display
unit -J255. The temperature sender -G150 is designed as an NTC sensor. The
resistance is evaluated as a signal from the control unit and regulates the air
distribution and delivery rate of the blower.
Measured value block 017
Display zone 1:
Readout of left vent
temperature sender -G150 in °C
Display zone 2:
Readout of right vent
temperature sender -G151 in °C
Display zone 3:
Readout of centre vent
temperature sender -G191 in °C
Display zone 4:
Display zone currently
J The value of
the out-flow temperature is determined as a reference signal to the dash panel
temperature sensor -G56 on the right and left sides.
J As the
temperature falls the electrical resistance increases.
J The sender is
self-diagnosis compatible. A fault detected in the sender is only registered by
the operating and display unit -J255 if the coolant temperature is detected as
J If the fault:
"short to earth" is detected by the operating and display unit -J255,
the value 150°C is entered in display zone 1 of measured
value block 017.
J If the fault:
"open circuit/short to positive" is detected by the operating and
display unit -J255, the value -70°C is entered in display zone 1 of measured
value block 017.
J If the left
vent temperature sender -G150 fails, the value of the intact vent temperature
sender -G151 is adopted. Operation is maintained.
J If both
senders (-G150 and -G151) fail, the air temperature downstream of the heat
exchangers can no longer be recorded and the temperature control fails. This
causes the heating power to be controlled in preset temperature increments by
the operating and display unit -J255, using a substitute value for each side.
shows that temperature senders are the most frequent cause of temperature control
faults. They do not usually fail immediately, but deliver false values to the
control unit based on an additional wire resistance as a result of damage or
corrosion in the connector contacts. Thus a comparison of the values of both
senders (-G150 and -G151) in the relevant display zones is recommended for
J A General Body
Repairs, Interior; Rep.Gr. 70; Removing and installing centre left vent sensor
J A Current flow