Vanden Plas L6-4.2L (1982)
Servo Control Unit Operation
Function:
To operate various microswitches, vacuum switches and air distribution flap linkage by means of a camshaft, on signal from the in-car and
ambient sensor, temperature selector and feedback potentiometer.
Location:
Behind R/H console kick panel and center console.
OPERATION
Depending upon the position of the temperature selector and temperature of the in-car sensor, the camshaft will rotate in either direction.
SERVO MOTOR
Function:
To drive camshaft in either direction upon signal from amplifier.
RECIRCULATION / HIGH SPEED MICROSWITCH
Function:
To allow high (4th) speed fan in full cooling mode when camshaft has moved to full cooling limit switch - operated by camshaft Cam S10.
RANCO OVERRIDE MICROSWITCH
Function:
To override Ranco thermostat in full cooling mode to allow minimum cool down time - operated by camshaft Cam S10.
FULL COOLING LIMIT MICROSWITCH
Function:
To limit maximum camshaft movement in full cooling mode - operated by camshaft Cam S1.
FULL HEATING LIMIT MICROSWITCH
Function:
To limit maximum camshaft movement in full heating mode - operated by camshaft Cam S2.
FAN SPEED MED 1 MICROSWITCH
Function:
MED 1 is 2nd fan speed - Signals through resistors to increase or decrease fan speed in cooling mode. Decrease fan speed in heating mode
depending upon rotational direction of camshaft (heating mode limited to Low and MED 1 speeds) - operated by camshaft Cam S3.
FAN SPEED MED 2 MICROSWITCH
Function:
MED 2 is 3rd fan speed, signals through resistors to increase or decrease fan speed in cooling mode - operated by camshaft Cam S4.
WATER TEMPERATURE OVERRIDE MICROSWITCH
Function:
Overrides water temperature transmitter when cooling mode is selected and engine water temperature is below 40°C (103°F).
In cooling mode this allows the fans and compressor to operate immediately - operated by camshaft Cam S5. Does not allow air
distribution to vehicle interior until water temperature is 40°C (103°F) - heating mode selected.
LINKAGE MOVEMENT
Function:
To place air distribution flaps in position depending upon selection at mode control and temperature selector.
Operation:
Upper heating, lower heating, lower cooling - operated by camshaft Cam S6.
VACUUM SWITCH A (Inner)
Function:
Closes heater water valve in full cooling mode - operated by camshaft Cam S7.
LINKAGE MOVEMENT
Function:
To place air distribution flaps in position depending upon selection at mode switch.
Operation:
Upper cooling flap - operated by camshaft Cam S8.
VACUUM SWITCH B (Outer)
Function:
Opens center dash flap in full cooling mode - operated by camshaft Cam S9.
FEEDBACK POTENTIOMETER
Function:
One member rotates with camshaft varying resistance. Provides a modified response to bias circuit to prevent hunting between heating and
cooling. Maintains a balanced electrical condition.
CAMSHAFT OPERATIONAL SEQUENCE - MODE CONTROL
OFF
1.
Vacuum solenoid energized - recirculation mode for fans
2.
No blower feeds
3.
Clutch disconnected
4.
No vacuum feeds so that:
(a)
hot water flows to heater matrix
