Vanden Plas L6-4.0L (1990)
Coolant Temperature Sensor / Switch HVAC: Technical Service Bulletins
A/C - Switch Revised
SECTION:
86
WATER TEMPERATURE SWITCH
No: 71
Model:
1990 MY SEDANS Date: APRIL, 1990
KEYPOINTS: REVISED SWITCH
Beginning with VIN 594576 (1990 M.Y.), the air conditioning/ heater water temperature switch has been revised in conjunction with electronic control
module circuitry changes.
SWITCH OPERATION:
^
Beginning with the above VIN, the operation of the switch has been changed from normally open when the coolant temperature is below 30~C, to
normally closed.
^
When the coolant is below 30~C, the switch is closed, supplying a ground to the ECU. This inhibits premature operation of the interior fans,
preventing cold air from being blown into the car.
^
When the coolant is above 30~C, the switch will open allowing the fans to operate normally.
NOTE:
The revised temperature switch (JLM 2121) and new electronic control module (DBC 4309) are not interchangeable with the previous
parts.
^
With the new system, if the temperature switch or the harness become open circuit, the fans will continue to operate even if the temperature is
below 30~C.
