Electrically Adjustable Front Seat With Memory
General description of operation
The memory operation means that the electrically operated seat is equipped with an electronic control module, a position sensor on each motor and a switch with four buttons for memory programming and operation.
The memory operation allows the possibility of storing three seat adjustments that the seat can than assume automatically when the button for the particular adjustment is held in.
From and including M94 it is also possible to operate the seat when the ignition key is in the OFF position and also when the respective door is opened.
This operation is achieved by the electronic control module, that reads the status of the interior lighting door switches.
From and including M95 the electrically operated front seat with memory is only used on the driver side.
Current Saab 9000 M96 introduce a new electronic control module with two connectors, A with pin 26 or with pin 8.
Memory operation
The button set for memory and memory programming operation consists of four buttons. Three memory buttons, "1", "2" & "3", and also a memory programming button "M". The seat adjustment is stored in the memory in the following way:
- Position the seat in the desired position using the regular switch.
- Store the adjustment position pressing the "M" button and one of the memory buttons "1", "2" or "3" at the same time.
- To recall the stored adjustment position press and hold the selected memory button until the desired seat position is achieved.
The electronic control module is supplied with voltage from +30 via a fuse 25 (LHS) and fuse 26 (RHS). The motors, switch and position sensors (potentiometers) are supplied with voltage from the electronic control module.
The electronic control module constantly reads the switches and then selects an appropriate combination of switches and the electronic control module carries out the corresponding operations. When the motors are activated, the electronic control module regulates the current consumption of each motor and checks the seat position via the position sensors.
The position sensors are potentiometers fitted on the particular motor shaft.
The potentiometers are measured with a 5v voltage. Form the electronic control module. When the motor is rotated the voltage at the center output varies between 0.4v and 4.6v. By measuring this voltage the electronic control module is able to decide the seat adjustment.
The M95 electronic control module and the M96 electronic control module (current production) have separate connectors for the particular motor and potentiometer according to the following:
- 4 x 2 pole connector for the motors.
- 4 x 3 pole connector for the potentiometers.
The earlier electronic control module have cable exits.
Important: Caution should be observed if any of the 2 or 3 pole connectors become free during fault diagnosis.
The connector terminals are not mechanically coded, only color coded. Incorrect connection can lead to faulty operation.
The switches consists of a number of circuit breakers (1 pole 2 way), that's polarity is measured by B+ from the electronic control module. When a switch contact is made B+ is measured at the appropriate switch intake on the electronic control module. The voltage then varies from 0 to approx. 12v.
The switches and the memory buttons are continually monitored by the electronic control module. When an appropriate choice of switch or memory button is detected, the electronic control module carries out the appropriate operation, that is to say, the motors are controlled manually or by the adjustment memory or the seat adjustment is stored in the memory function.
Inappropriate choice of switch or memory button, for example pressing several memory buttons or more than two switches at the same time results in no operation. Selecting the memory programming or the memory adjustment at the same time results in the activation of the manual setting.
Manual setting of seat adjustment
At manual setting of the seat adjustment the electronic control module reads from the selected switch and then supplies current to the appropriate motor.
The electronic control module only allows two motors to be driven at the same time, that are stopped if more than two switches are selected on the manual control unit at the same time. The electronic control module supplies current to these motors as long as the particular switches on the manual control unit are selected (maximum 1 minute).
The back rest has no mechanical stop to limit its inclination forwards and backwards. The limitation is decide by the electronic control module by reading the back rest position sensor. The electronic control module does not permit the back rest motor to operate if its position sensor is faulty.
Memory setting of seat adjustment
Electronic control module reads all the position sensors and stores their readings in an internal seat memory. The seat memory is none-volatile and stores information even when the electronic control module is without voltage.
If any of the position sensors is faulty the new seat adjustment is not stored in the seat memory, without a possible earlier memorized seat adjustment setting remaining after settings in the memory.
Memory adjustment
The electronic control module reads all the position sensors and guides the seat motor adjustments in correspondence with the adjustment stored in the seat memory, or until the memory switch is released.
If the electronic control module detects any fault in any of the position sensors or if the seat slowly moves itself in any way, the corresponding motor is stopped.