Lumbar Support (With RPO Code A45)

LUMBAR SUPPORT DESCRIPTION AND OPERATION (WITH RPO CODE A45)

The driver lumbar support system consist of the following components:
- Power Lumbar Switch
- Memory Seat Module (MSM)
- Lumbar Horizontal Motor
- Lumbar Vertical Motor
- Lumbar Horizontal Position Sensor
- Lumbar Vertical Position Sensor
- The MEM/RFA Fuse 10 A

Power Lumbar Switch
Battery positive voltage is supplied at all times to the lumbar switch from the MEM/RFA Fuse located in the rear fuse block. When the lumbar switches are pressed they send a 12-volt signal to the memory seat module (MSM). The MSM commands the lumbar motors to move in response to the switch inputs.

Motors
The lumbar motors operate independently of each other. Each motor contains a electronic circuit breaker (PTC) which will reset only after voltage has been removed from the motor. Both, the driver and passenger seat back contain two lumbar motors (horizontal and vertical). The lumbar horizontal motor moves the lumbar in the forward and rearward directions and the lumbar vertical motor moves the lumbar in the up and down directions. The memory seat module (MSM) provides each motor with a soft stop that will actually stop the motor just before its physical end-of-travel. This decreases the stress on each motor. If a motor reaches the end-of-travel due a soft stop and the switch is released and pressed again, the lumbar will move short distance farther to the physical travel limit.

Lumbar Horizontal Movement
When the lumbar switch is operated to move the lumbar forward, battery positive voltage is applied through the switch contacts and the driver seat lumbar forward switch signal circuit to the memory seat module (MSM). In response to this signal, the MSM applies battery positive voltage through the driver seat lumbar motor forward control circuit and ground through the driver seat lumbar motor rearward control circuit to the horizontal motor. The motor runs to drive the lumbar forward toward the occupant's back until the switch is released. Moving the lumbar rearward works similarly to moving the lumbar forward, except that battery positive voltage and ground are applied on the opposite circuits causing the motor to run in the opposite direction. The MSM also controls the lumbar horizontal motor during memory recall functions.

Lumbar Vertical Movement
When the lumbar switch is operated to move the lumbar up, battery positive voltage is applied through the switch contacts and the driver seat lumbar up switch signal circuit to the memory seat module (MSM). In response to this signal, the MSM applies battery positive voltage through the driver seat lumbar motor up control circuit and ground through the driver seat lumbar motor down control circuit to the horizontal motor. The motor runs to drive the lumbar up until the switch is released. Moving the lumbar down works similarly to moving the lumbar up, except that battery positive voltage and ground are applied on the opposite circuits causing the motor to run in the opposite direction. The MSM also controls the lumbar vertical motor during memory recall functions.

Position Sensors
The lumbar position sensors are potentiometers which are attached directly to each lumbar motor. The memory seat module (MSM) supplies a 5-volt reference voltage via the 5-volt reference circuit and ground via the low reference circuit to the respective lumbar position sensors. When the motor rotates, the resistance of the potentiometer varies changing the feedback voltage of the position sensor signal circuit. The voltage varies from 0.25-4.75 volts. The MSM monitors this voltage signal to determine the position of the lumbar. When a memory set command is received, the MSM records the lumbar position by storing the feedback voltage from each position sensor. Then when a memory recall command is received, the MSM moves the motors until the position sensor feedback voltages equals the feedback voltages stored in memory. The lumbar support is not involved in the easy exit function.

Memory Functions
Refer to Memory Seats Description and Operation.