Power Seats

Figure 15-24. The motor in this door can raise and lower the window. (GM Service and Parts Operations)

nected to one of the two motor brushes. The window is moved up or down by reversing the direction of motor rotation. Motor rotation is controlled by routing current into one brush or the other. Each individual window switch is connected in series with the driver’s master switch. Current from the motor must travel through the master switch to reach ground.

Electrically adjustable seats can be designed to move in several ways, as follows: • Two-way systems move forward and backward. • Four-way systems move forward, backward, and front edge up and down. • Six-way systems, used in most late-model applications, move the entire seat forward, backward, up, and down; tilt the upper cushion forward and backward, and move the lower cushion front edge up and down, and rear edge up and down.

GM makes a typical two-way power seat system, as shown in Figure 15-26. The seriesconnected motor has two electromagnetic field windings that are wound in opposite directions. One winding receives current from the forward switch position. The second winding receives current from the rear switch position. Current through one winding will make the motor turn in

Figure 15-25. Typical power window control circuit.

(DaimlerChrysler Corporation)

Figure 15-26. A GM two-way power seat has a motor with electromagnetic fields; current through the fields determines the direction of the motor and thus the

movement of the seat. (GM Service and Parts Operations) one direction; current through the opposite winding will make the motor turn in the opposite direction. The motor armature is linked to the seat mounting by a transmission that translates this rotary motion into seat motion.

Ford and GM have made four-way power seat systems that contain two reversible motor armatures in one housing. Ford’s motors have permanent-magnet fields, while GM’s motors have series-connected electromagnetic fields. One motor is linked to a transmission that moves the seat forward and backward. The other motor’s transmission tilts the front edge of the seat. Asingle four-position switch controls both motors. The switch contacts shift current to different motor brushes (Ford) or to different field windings (GM) to control motor reversal.

Early GM six-way power seat systems useone reversible motor that can be connectedtoone of three transmissions. Transmissionhookup is controlled by three solenoids (Figure 15-27). The control switch is similar tothat used by Ford and Chrysler, but the circuitry differs. Current must flow through one ofthesolenoids to engage a transmission, then through a relay to ground. The relay points conduct current to the motor brushes. Additional switch contacts conduct current to the electromagnetic motor windings.

Chrysler, Ford, and late-model GM six-way power seat systems use three reversible motor

Figure 15-27. GM’s early six-way power seat systems use one reversible motor that can be connected to one of three transmissions. Transmission hookup is controlled by three solenoids. (GM Service and Parts

Operations)