Pressure Switch Manifold
The pressure switch manifold (PSM) is a multiple-switch assembly made up of three N/O pressure switches and one N/C pressure switch. N/O pressure switches (4, 3 and 2) correspond to shift valves C, D and E. Fluid pressures are fed from shift valves C, D, and E, to the manual selector valve and to the pressure switches based on the positions of the valves and shift selector. The shift valve fluid pressures reflect the logic condition at the corresponding solenoids. This logic indicates the current transmission operating range to the TCM.
The three fluid pressure switches corresponding to the shift valves are N/O, contacts not touching, when no fluid pressure is present, so that electrical current is stopped at the switch. When fluid pressure is routed to the switch, it moves the diaphragm and upper contact so that the contact element touches both the positive and ground contacts. This closes the circuit and allows current to flow from the positive contact and through the switch.
The pressure switch (1) corresponding to REVERSE is N/C, since fluid pressure is always present unless the selector valve is moved to REVERSE. The PSM also contains a temperature sensor thermistor (5) for sump temperature. Changes in sump fluid temperature are indicated by changes in sensor resistance. Increasing temperature causes decreased sensor resistance. The resistance value is then relayed to the TCM as an input for shift control.