A/T - Governor Pressure Switches

TSB 86-9 (Feb)

SUBJECT: GOVERNOR PRESSURE SWITCHES

Often there is a need for pressure switches of a higher pressure rating than is available. (Such as on a 125C & 200C -- S-10, Camaro, Firebird & others)




Most switches of this type have a 1/16" allen screw inside, and can be adjusted. (See illustration)

Carefully dig away the epoxy seal over the contact rivet to expose the screw, and clean the threads as much as possible with a 90° scribe. If the screw is stuck, a small amount of heat (often a lighted match is enough) will usually free the screw.

Turning the screw in (clockwise) will increase the pressure rating, and thereby increase the L/U (lock-up) point.

Shops that do not have an air regulator can test the switch adjustment with the vehicle in the air, as follows:

A. Unplug the harness connector from the transmission case connector.

B. Connect one lead of an ohmmeter to the "A" terminal of the case connector, and the other lead to the case, or pan.

C. Run the vehicle speed up until the ohmmeter reads continuity. That is the new speed at which the TCC will engage.

Fluid will not usually leak at the screw. You may want to cover it again with epoxy, once it has been set, to keep the screw from backing off, and to ensure against a leak.

THERE ARE ALSO NUMEROUS REPORTS OF NEW SWITCHES THAT HAVE THE WRONG RATING ON THEM.

CAUTION:
You might want to buff the old PSI rating off the switch. Someday that switch might find its way back into your shop, and "haunt" you with the wrong rating on it.