Troubleshooting 6-way Adjustable Power Seats

Proper Parts gratefully acknowledges Cadillac Tim as the source of this article. When this article was published his website CadillacTim.com was offline.

Six way power seats have six components: switch, motor relay, seat motor, seat transmission, cables, and seat tracks.

Operation

Battery power is fed to the switch and to the seat relay. Both the seat motor and the seat transmission are grounded to the seat frame, which in turn is grounded to the floor by a ground wire.

When a button on the switch is activated, battery power is sent to the seat relay and to the seat transmission.

When power is sent to the relay, the contacts close and power is sent to the seat motor. The motor runs in opposing directions depending on which side of the relay receives battery power. The power sent to the transmission engages a solenoid which in turn engages a transmission shaft to which a cable is attached. This cable turns an actuator in the seat track, moving the seat. The seat moves in opposing directions depending on which switch button is pushed.

Components

NOTE: Wire insulation colors are italicized to reflect that more than one wire color scheme was used during production, so that the wire colors in this guide may be different than the wire colors in your 6-way adjustable power seats.

Switch

The switch has six terminals as depicted below. The power feed is an orange and black wire. Above this terminal in a horizontal line are the three seat transmission terminals. At the far end there are three terminals “stacked” diagonally. The middle terminal is part of the seat transmission group previously mentioned. The terminals directly above and below this control the seat motor relay.

O motor

O seat xmission O seat xmission O seat xmission

O power feed O motor

Seat motor relay

The seat motor relay is located under the seat, attached to the seat motor assembly. It has six terminals as depicted below. The lower four terminals are connected together in pairs. The seat motor ground wires are attached to the bottom of this relay. Depending on which side of this relay is grounded, the motor moves forward or backward. The power feed is the terminal directly above this group of four, and the top terminal is the battery feed to the motor. When the relay is energized, the power goes from the power feed to the top terminal which operates the motor.

O battery feed to motor

O power feed

O to "motor" terminal on switch O to "motor" terminal on switch

O GND to terminal above O GND to terminal above

Seat Motor

Three wires extend from the seat motor. The red wire is positive and is connected to the top terminal of the relay. The seat motor is grounded through the seat frame. It is energized when the ground circuit of the relay (lower portion of relay) receives current from the switch. This in turn sends battery voltage to the top terminal of the relay, which powers the motor. When the yellow wire is receives power, the motor moves backward. When the green wire receives power, the motor moves forward.

Seat Transmission

The seat transmission has three solenoids in it. When one or two of these solenoids are energized, they push gear(s) into the main drive (driven by the seat motor). When these gears engage they spin shafts to which the cables are connected. These three shafts (one per solenoid) are continuous, and the cables connect on each end. Therefore, each shaft controls two seat cables. One shaft controls forward and backward, another shaft controls front tilt, and the third shaft controls rear tilt. The transmission solenoids are energized by the seat switch. The transmission is grounded through the seat frame.

Cables

There are six seat cables, three on each side of the transmission. They operate in pairs, and are engaged when the transmission solenoid shafts are turning. These cables turn the actuators in the seat tracks, thus moving the seat.

Seat tracks

There are two seat track assemblies (one each side). Each track assembly has three actuators. The middle actuator controls forward and backward movement, the front actuator controls front tilt, and the rear actuator controls rear tilt. These actuators are driven by the seat cables.

Common power seat problems

When I operate the switch nothing happens, no sound at all.

A common problem that causes this is a broken wire, a bad ground, or a bad switch. If the car has been sitting for a long time, corrosion can build up at the wire connections, and at the point where the motor and the seat transmission bolt to the seat frame. Try connecting a jumper ground wire from the motor case to the car body and see if anything changes. Connect a jumper wire from the seat transmission to the car body and listen for a “clicking” sound. If the motor runs, or you hear the clicking sound, unbolt the motor and transmission and clean up where they bolt to the frame.

If you try this and still nothing happens, confirm that you are getting battery voltage to the seat relay. An easy way to check this is to put your hand on the relay and “feel” for the relay to click when you engage the switch. If the relay clicks, and the ground is okay on motor, check for battery voltage at the red wire (top of relay) when the relay clicks. If voltage is present, but the motor does not operate, then the motor is defective.

If you do not get battery voltage from the switch to the relay or transmission, check for a bad connector at the switch, or broken wires (especially between the door and body when the switch is mounted on the door armrest). If voltage is present at the switch, but not at the relay or transmission, then the switch may be bad.

I hear a “click,” but no seat motor running.

Confirm that battery power is sent to the seat relay. An easy way to check this is to put your hand on the relay and “feel” for the relay to click when you engage the switch. If the relay clicks, and the ground is okay on motor, check for battery voltage at the red wire (top of relay) when relay clicks. If voltage is present, but the motor does not operate, then the motor is defective.

The motor runs, but no seat movement.

Check for bad ground on seat transmission. If ground is okay, check for battery voltage to the terminals going into the seat transmission. If voltage is present when switch is operated, and ground is okay, then the seat transmission is defective.

The seat moves in certain directions, but not all.

The most common problem is defective or stuck solenoid in the seat transmission. Could also be a bad connection on a particulr terminal at the seat switch, or a bad contact in the switch.

Seat tries to move, but stops. One side of seat works, other does not.

Could be broken or stuck seat cable, bad actuator in seat track, or rusted seat track. If the seat moves very slowly, most likely the motor is weak and needs to be replaced.