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BMW E39 Power Seat Testing
 
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Pelican Technical Article:

BMW E39 Power Seat Testing

Kerry Jonsson

Time:

4 hours4 hrs

Tab:

$0

Talent:

****

Tools:

Multi-meter, test leads, fused jumper wires, door panel removal tool,

Applicable Models:

BMW E39 5-Series (1997-03)

Parts Required:

Power seat switch, seat side covers

Hot Tip:

You can do all of this testing on the manual power seats without using a scan tool

Performance Gain:

Get manual seats to function properly

Complementary Modification:

Replace faulty power seat switches

If you are the only driver of the car you may not notice for quite some time that the seat may no longer be working, You usually do not have to make any adjustments when the same person gets in and out of the car. Sometimes things we handle in the car fall in between the seats. If it's metal like change it can get caught in the seat mechanism and cause it to jamb. For whatever reason, if your seats stop working you are going to want to get them working again. In this tech article we are going to go over the steps to test manual electric seats. If you have driver seat memory control that is going to be covered in a separate article. That system is controlled by a memory seat module. I this article we will be using the passenger side seat for the manual electric seat testing. A manual electrical driver seat is nearly identical but you should have a wiring diagram for your specific car.

To access the power seat switch for the seat you are working on remove the seat side cover. The steps for removing this cover are found in the tech article front and rear seat removal. Follow only the steps that show you how to remove the side seat covers.

Here we are at the passenger power seat switch.
Figure 1

Here we are at the passenger power seat switch. Grab the seat bottom position switch and pull off the plastic knob by pulling it away from the seat.

Pull off the seat back switch knob by pulling it away from the switch.
Figure 2

Pull off the seat back switch knob by pulling it away from the switch.

Pull out the seat side cover to expose the inside of it.
Figure 3

Pull out the seat side cover to expose the inside of it. Unclip the 4 plastic tabs (green arrows) that hold the switch to the cover. You can see the top two but the bottom two are hidden underneath the switch in this picture.

With the switch exposed identify the 3 black pins that operate the switch.
Figure 4

With the switch exposed identify the 3 black pins that operate the switch. The first pin (green arrow) is for the front seat cushion up and down and forward and back movement. The second pin (yellow arrow) is for moving the whole seat up and down and forwards and backwards. The third pin is for positioning the seat back and the headrest.

If the seat is not working at all check the fuse.
Figure 5

If the seat is not working at all check the fuse. Here we are at the fuse box mounted in the ceiling of the glove box. We have the glove box removed here but you donÂ't have to remove the glove box. On our model it is fuse #10 (green arrow) in the fuse box.

To unplug the passenger power seat switch from the harness grab the slide lock and pull it away from the switch.
Figure 6

To unplug the passenger power seat switch from the harness grab the slide lock and pull it away from the switch. It is a cam lock so as you slide it out the switch and harness and switch will separate until you can unplug the switch.

With the power seat switch unplugged you can see the pins.
Figure 7

With the power seat switch unplugged you can see the pins. Check for corrosion that might be causing a bad connection.

This is the back of the power seat switch unplugged.
Figure 8

This is the back of the power seat switch unplugged. If you look closely you can see the pin numbers embossed in the plastic next to each pin. Here in this tech article we are going to give you the pin numbers.

With a prying tool lever off the back cover to expose the wiring while the switch is still connected.
Figure 9

With a prying tool lever off the back cover to expose the wiring while the switch is still connected. Now we can test the switch.

Here is what the wiring and pin connections look like with the back cover off.
Figure 10

Here is what the wiring and pin connections look like with the back cover off. You should not remove the back cover with the switch unplugged because the pins may fall out of the connector and you will have to be able to identify the correct slots for the pins to go back into.

In this picture the green arrow identifies pin 1, power or ground for seat cushion tilt motor
Figure 11

In this picture the green arrow identifies pin 1, power or ground for seat cushion tilt motor

In this picture the green arrow identifies pin 2, power or ground for seat cushion tilt motor
Figure 12

In this picture the green arrow identifies pin 2, power or ground for seat cushion tilt motor

In this picture the green arrow identifies pin 3, power or ground for the seat forward and back motor
Figure 13

In this picture the green arrow identifies pin 3, power or ground for the seat forward and back motor

In this picture the green arrow identifies pin 4, power or ground for the seat forward and back motor
Figure 14

In this picture the green arrow identifies pin 4, power or ground for the seat forward and back motor

In this picture the green arrow identifies pin 5, power supply to the switch
Figure 15

In this picture the green arrow identifies pin 5, power supply to the switch

In this picture the green arrow identifies pin 6, ground supply for the switch.
Figure 16

In this picture the green arrow identifies pin 6, ground supply for the switch.

In this picture the green arrow identifies pin 7, power or ground supply for the seat up and down motor
Figure 17

In this picture the green arrow identifies pin 7, power or ground supply for the seat up and down motor

In this picture the green arrow identifies pin 8, power or ground supply for the seat up and down motor
Figure 18

In this picture the green arrow identifies pin 8, power or ground supply for the seat up and down motor

In this picture the green arrow identifies pin 9, power or ground for the headrest motor
Figure 19

In this picture the green arrow identifies pin 9, power or ground for the headrest motor

In this picture the green arrow identifies pin 10, power or ground for the seat back motor
Figure 20

In this picture the green arrow identifies pin 10, power or ground for the seat back motor

In this picture the green arrow identifies pin 11, power or ground for the headrest motor
Figure 21

In this picture the green arrow identifies pin 11, power or ground for the headrest motor

In this picture the green arrow identifies pin 12, power or ground for the seat back motor
Figure 22

In this picture the green arrow identifies pin 12, power or ground for the seat back motor. Each motor that controls the power seats is a DC reversible motor. This means it has only 2 wires. When one wire is power and the other wire is ground the motor will move the seat in one direction. If you reverse the polarity and apply ground to the first wire and power to the second wire the motor will spin and operate the seat in the opposite direction. We are going to connect our test leads to each wire of the motor we are testing. If we get a good voltage reading then the switch is good and the motor is bad. If we do not get a good voltage reading then we have a bad switch or possibly bad wiring.

Here we are at the back of the switch and we have our red lead on pin #5 (power supply) and our black lead on pin #6 (ground supply.
Figure 23

Here we are at the back of the switch and we have our red lead on pin #5 (power supply) and our black lead on pin #6 (ground supply.

You should read battery voltage on your meter.
Figure 24

You should read battery voltage on your meter. This means fuse #10 is good in the fuse box.

Here we are testing the seat back switch.
Figure 25

Here we are testing the seat back switch. Move your test leads to pins #10 and #12 at the back of the switch. It does not matter which lead goes on which pin. Because of the reverse polarity you are going to read either battery voltage or negative battery voltage depending on which way you move the switch.

Put the seat switch knobs back on the switch temporarily.
Figure 26

Put the seat switch knobs back on the switch temporarily. Push the seat back switch forward in the direction of the blue arrow.

Your meter should read either positive battery volts or negative battery voltage.
Figure 27

Your meter should read either positive battery volts or negative battery voltage. In our case it reads positive battery voltage, and the seat moved forward.

Move the seat back switch in the backwards direction in the direction of the blue arrow.
Figure 28

Move the seat back switch in the backwards direction in the direction of the blue arrow.

Your meter should read the opposite voltage reading you got from the first test.
Figure 29

Your meter should read the opposite voltage reading you got from the first test. This means the voltage is going through the motor in the opposite direction. In our case we measured negative battery voltage and moved our seat back backwards.

Here we are testing the headrest switch.
Figure 30

Here we are testing the headrest switch. Move the test leads to pin# 9 and pin# 11. Once again it does not matter which lead goes where.

Move the seat back switch in the up position in the direction of the blue arrow.
Figure 31

Move the seat back switch in the up position in the direction of the blue arrow.

Your meter should read either positive battery volts or negative battery voltage.
Figure 32

Your meter should read either positive battery volts or negative battery voltage. In our case it reads positive battery voltage, and the headrest moved up.

Move the seat back switch in the down position in the direction of the blue arrow.
Figure 33

Move the seat back switch in the down position in the direction of the blue arrow.

Your meter should read the opposite voltage reading you got from the first test.
Figure 34

Your meter should read the opposite voltage reading you got from the first test. This means the voltage is going through the motor in the opposite direction. In our case we measured negative battery voltage and moved our headrest in the downward direction.

Here we are testing the seat up and down switch.
Figure 35

Here we are testing the seat up and down switch. Move the test leads to pin# 7 and pin# 8. Once again it does not matter which lead goes on which pin.

Use the seat switch to move the seat in the up position, in the direction of the blue arrow.
Figure 36

Use the seat switch to move the seat in the up position, in the direction of the blue arrow.

Your meter should read either positive battery volts or negative battery voltage.
Figure 37

Your meter should read either positive battery volts or negative battery voltage. In our case it reads positive battery voltage, and the whole seat moved up.

Use the seat switch to move the seat in the down position, in the direction of the blue arrow.
Figure 38

Use the seat switch to move the seat in the down position, in the direction of the blue arrow.

Your meter should read the opposite voltage reading you got from the first test.
Figure 39

Your meter should read the opposite voltage reading you got from the first test. This means the voltage is going through the motor in the opposite direction. In our case we measured negative battery voltage and moved the whole seat downward direction.

Here we are testing the forward/backward seat switch.
Figure 40

Here we are testing the forward/backward seat switch. Move your test leads to pin# 3 and pin# 4. Once again it does not matter which lead goes on which pin.

Use the seat switch to move the seat in the forward position, in the direction of the blue arrow.
Figure 41

Use the seat switch to move the seat in the forward position, in the direction of the blue arrow.

Your meter should read either positive battery volts or negative battery voltage.
Figure 42

Your meter should read either positive battery volts or negative battery voltage. In our case it reads positive battery voltage, and the whole seat moved forward.

Use the seat switch to move the seat in the rearward position, in the direction of the blue arrow.
Figure 43

Use the seat switch to move the seat in the rearward position, in the direction of the blue arrow.

Your meter should read the opposite voltage reading you got from the first test.
Figure 44

Your meter should read the opposite voltage reading you got from the first test. This means the voltage is going through the motor in the opposite direction. In our case we measured negative battery voltage and moved the seat in the rearward direction.

Here we are testing the front seat up and down switch.
Figure 45

Here we are testing the front seat up and down switch. Move your test leads to pin# 1 and pin# 2. Once again it does not matter which lead goes on which pin.

Use the seat switch to move the front of the seat in the up position, in the direction of the blue arrow.
Figure 46

Use the seat switch to move the front of the seat in the up position, in the direction of the blue arrow.

Your meter should read either positive battery volts or negative battery voltage.
Figure 47

Your meter should read either positive battery volts or negative battery voltage. In our case it reads positive battery voltage, and only the front of the seat moved up.

Use the seat switch to move the front of the seat in the down position, in the direction of the blue arrow
Figure 48

Use the seat switch to move the front of the seat in the down position, in the direction of the blue arrow

Your meter should read the opposite voltage reading you got from the first test.
Figure 49

Your meter should read the opposite voltage reading you got from the first test. This means the voltage is going through the motor in the opposite direction. In our case we measured negative battery voltage and moved only the front of the seat in the downward direction. Remember, if we get a good voltage reading then the switch is good and the motor is bad. If we do not get a good voltage reading then we have a bad switch or possibly bad wiring. When reassembling the various components be careful to route the wiring as you found it. You donÂ't want door covers or seat operation to get caught or rub against wiring.

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Page last updated: Fri 12/9/2016 02:05:24 AM