Fluid Pressure Sensor/Switch: Description and Operation

PURPOSE
The transmission overload protection switches protect the shift elements of the automatic transmission from thermal overload. This can occur during gearshifts under load in the high RPM range.

Overload Protection Switch (S65) For Brake Band "B1":

SWITCH FOR BRAKE BAND B1

Overload Protection Switch (S65/1) For Brake Band "B2":

SWITCH FOR BRAKE BAND B2

LOCATION
The overload protection switches are mounted into the transmission housing.

DESIGN
This component is designed as a pressure switch and mounted into the hydraulic circuit of brake bands "B1" and "B2".

OPERATION
The switch is open at a hydraulic circuit pressure less than 1.8 bar.
The switch is closed at a hydraulic circuit pressure exceeding 1.8 bar.
If overload is detected, the ignition is retarded for approx. 400 ms to 5° BTDC to reduce engine torque. Protection switch S65 (for brake band "B1") protects the transmission during 1>2 or 2>3 upshifts. Protection switch S65/1 (for brake band "B2") protects the transmission during 3>4 upshifts or 4>3 downshifts.