My gear shifter will often not shift unless I depress the Gear Shift Lock Release button adjacent to the gear shifter.

Could this possibly be the Brake Pedal Positioning Sensor? Any caveats on replacing the unit since once I remove it from the front of the master cylender the vaccum seal is broken.

Thanks in advance,
Armando Flores
af1023@yahoo.com

http://volvospeed.com/Repair/Microswitch.htm
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Dennis

This is possible. The switch is inside the car near the top of the brake pedal. The switch has two poles, one for the brake light and the other one is for the Gear Shift Lock release. Mine failed also. It is easy to see it and replaced it. Removed the panel under the dash. You will see the switch near the top of the brake pedal.

Note: The switch position is adjustable. Are your brake light working properly?

The brake lights work fine. However, the unit I am speaking of sits on front of the Vaccum Booster and has an electrical conecter with two poles.

Pedal position sensor on the brake booster has nothing to do with shift lock or brakelights. It is only input info on pedal position for ABS. Shift lock is controlled by brake light switch and micro switch at shifter. When shifter is in park, micro switch on shifter is closed. When brake pedal is depressed, current flows from the switch through the closed micro switch and on to the solenoid. When out of park, open micro switch prevents solenoid activation evety time brakes are used. Common failures are micro switch, light switch at pedal, and electrical portion of ignition switch.

Bob has it right, there was even a recall on 850's, late model 940s and 960's called recall 76, which has to deal with replacing the shift lock mircro switch. I cannot remeber if the 93 850 had a mirco switch or a solenoid down near the shifter (called the "gear lever carrier" according to volvo terms).