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BMW E39 Power Window Testing
 
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Pelican Technical Article:

BMW E39 Power Window Testing

Kerry Jonsson

Time:

4 hours4 hrs

Tab:

$0

Talent:

****

Tools:

Multi-meter, test leads, fused jumper wires

Applicable Models:

BMW E39 5-Series (1997-03)

Parts Required:

Door panels, window switches, window motor

Hot Tip:

You can do most of this testing without using a scan tool

Performance Gain:

Get all windows to function properly including automatic functions

Complementary Modification:

Identify if the problem is in the computer control or the window motor

You know how frustrating it can be when you go to open a window and it does not work at a place like a tollbooth. Sometimes you just want to outside air and not the air conditioning. Whatever the reason you want your power windows to work but you may not know what the problem is. Is it a switch problem? Is it the motor? Is it a wiring problem? In this tech article we are going to go over some basic testing and methods you can use to diagnose the problem(s).

The first step in any diagnostic procedure it to find out what is working and what is not.
Figure 1

The first step in any diagnostic procedure it to find out what is working and what is not. You may have noticed your driversÂ' side window is not working from the driversÂ' side switch. Is it a bad switch? Well you can check to see if the other windows are not working from the driversÂ' window switch. If the switch works the other motors then you probably just have a bad power window motor. If none of the windows will work you may have a blown fuse, bad drivers window switch or a bad body module (GEM). If the door panel is removed we can test the motor and eliminate that as a problem. If one of the other windows is not working try testing them from their individual switch. Keep in mind there is a cut-off switch for the rear power windows and that blocks the rear window switches from operating the rear windows. Make sure the driverÂ's door switch is set to allow the rear window switches to work.

The second step in diagnosing something that doesnÂ't work is to check the fuses.
Figure 2

The second step in diagnosing something that doesnÂ't work is to check the fuses. In our case of the 1997 E39 the two fuses that power up the power window system are fuses 6 and 29.Pictured here is the fuse box with fuses 6 and 29 indicated (red arrow). Unplug the fuse and see if it is blown. If it is, replace it with a known good one and see if you power windows start working. If you operate the power windows and the fuse blows then you have a short circuit somewhere in the car. Short circuits are difficult to find for experienced technicians let alone DIYÂ's. A short circuit is when the voltage supply does not make it to the consumer because it takes the short path directly to ground. You can use a short finder to locate the short. Follow the instructions on your short finder tool to find the problem and then fix it by insulating the damaged wire from the body ground. If each power window is working from their own individual switch but not the driverÂ's side switch you may want to check the connections at the driverÂ's power window switch. For the procedure to remove and unplug the switch see the removing door panel tech article.

Now that you have exposed the switch you can check that the electrical connections are plugged in properly.
Figure 3

Now that you have exposed the switch you can check that the electrical connections are plugged in properly. To check if any of the motors are working properly you need to remove the door panel of the window motor you want to test. In this case we have removed the right rear door panel but the procedure applies to all doors. To remove the door panel of the motor you want to test follow the procedures in tech articles for the front or rear door panels. The power window motors are DC reversible motors. This means that with voltage supplied on one wire and ground on the other wire the motor moves in one direction. If you reverse the polarity, meaning you switch with wires with power and ground the motor will move in the reverse position.

Install test pins and attach your red positive test lead (green arrow) and your black test lead (yellow arrow) to the power motor wiring so you can measure the direction of voltage to your motor.
Figure 4

Install test pins and attach your red positive test lead (green arrow) and your black test lead (yellow arrow) to the power motor wiring so you can measure the direction of voltage to your motor. It does not matter which wire on the motor you pick for the red and black lead because the voltage can go in either direction.

Turn on the ignition key and operate the power window switch from both the driverÂ's door switch and the door switch in the door itself.
Figure 5

Turn on the ignition key and operate the power window switch from both the driverÂ's door switch and the door switch in the door itself. If you removed (it) to pull off the door panel simply plug it back in. Push the switch in the direction of the blue arrow and look at the voltage reading of the meter. In our case we see the approximately correct volts going to the motor. This means the electrical signal is making it to the motor. This means the switch and the body module (GEM) are good and the motor or the connection at the motor is the problem. If you hear the motor working but the window does not go up and down then itÂ's the window regulator that is broken.

Push the power window switch in the direction of the blue arrow and you should see the voltage on the motor reverse.
Figure 6

Push the power window switch in the direction of the blue arrow and you should see the voltage on the motor reverse. This means power and ground are reversed through the motor. Notice the negative symbol in the meter screen. This indicates the voltage in the motor has reversed and the motor should operate in the other direction. If the motor is not moving then the motor or the connector is bad. If you can hear the motor moving but the glass is not going up of down then the regulator is bad.

You can use a fused jumper wire (red arrow) to run power and ground directly from the battery to the motor.
Figure 7

You can use a fused jumper wire (red arrow) to run power and ground directly from the battery to the motor. When you apply voltage to one wire and ground to the other wire the motor should move in one direction. If you reverse the leads the voltage should pass through the motor in the opposite direction and the motor should spin in the opposite direction. You must be careful not to let the power and ground supplies to touch. This will result is a short circuit and you will see a large spark and the fuse in your jumper will blow. You can use electrical tape to help prevent the wires from touching. Also never put your hand in the doorframe while you are operating the power window motor. You could get caught in the mechanism and really hurt yourself.

 Power Window Switch Testing: To remove the power window switch refer to the tech articles on removing the door panel for the door you are working on. Each power window switch operates the same except for the driverÂ's window switch, which is built into the driverÂ's door control module, therefore these switch contacts cannot be tested without a scan tool capable of talking to the GEM (body module).
The power window switch has 4 wires.
Figure 8

The power window switch has 4 wires. Starting from left to right pin# 1 (in this case a brown wire) is your ground (green arrow), pin# 2 (grey/red) is the power supply for illumination, pin# 3 and pin# 4 (grey/blue and grey/yellow) are for the up and down switches.

Connect the black lead of your meter to pin# 1 and the red lead to pin# 3.
Figure 9

Connect the black lead of your meter to pin# 1 and the red lead to pin# 3. You should not read any voltage. When you turn on the light switch the voltage should increase to about battery volts. This is the power supply to light the switch up. These switches have two positions in either the open or closed position. A slight push commands the window open until you release the switch (manual feature). Push the switch to the second position (a little harder) and the motor will continue to operate until it is all the way down (automatic feature). In the rest position there should be battery volts on both pins# 1 and #2. The voltage on pin#2 drops when you open the window and the voltage on pin#1 drops when you close the window. When you apply the automatic feature in the open position first pin# 2 will go to ground in the manual position and pin# 1 will also go to 0volts in the automatic position. When you apply the automatic feature in the close position first pin# 1 will go to 0volts in the manual position and pin# 2 will also go to 0volts in the automatic position. In review, when the GEM (body module) sees the voltage on pin#2 drop to ground first it starts to open the window and when it sees the voltage drop on pin# 1 it opens the window in the automatic feature. When the GEM sees the voltage drop on pin# 1 it starts to close the window and when it sees the voltage drop on pin# 2 it closes the window in the automatic feature.

Test the voltage on pin# 2.
Figure 10

Test the voltage on pin# 2. You should start with 12volts. In the manual open position the voltage should drop to 0volts. It will also drop to 0volts in the automatic close position.

Test the voltage on pin# 1.
Figure 11

Test the voltage on pin# 1. You should start with 12volts. In the manual close position the voltage should drop to 0volts. It will also drop to 0volts in the automatic open position.

Pin# 4 (green arrow) is the ground for the switch.
Figure 12

Pin# 4 (green arrow) is the ground for the switch. Pin# 3 (yellow arrow) is the voltage supply for the illumination bulb. Pin# 2 and pin# 1 (red and purple arrows respectively) are the window switch inputs to the body module. Keep in mind; if you check the switch operation and it is working but there is no voltage signal to the motor the GEM may be bad, you have broken wiring or a combination of the two. When reassembling the various components be careful to route the wiring as you found it. You donÂ't want door panels or window operation to get caught or rub against wiring.

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Comments and Suggestions:
Rodger Comments: It looks like I should ignore the Fig 8 pin numbers and just look at the Fig 12 pin numbers. Thanks for doing this write up. It answered all my questions.
March 27, 2016
  Followup from the Pelican Staff: Thanks for the follow up. We appreciate it.
- Nick at Pelican Parts
 
Rodger Comments: I got confused with the pin numbers. At Figure 8 you stated that #2 grey/red is for illumination. Then at Figure 9 you say that #3 will change voltage when the lights are turned on and at rest there is voltage to #1 and #2. It seems that pin #3 is for illumination and pins #2,4 are switched. Is that right?
March 27, 2016
  Followup from the Pelican Staff: I will have that corrected, it looks to have an issue with fig 8.

if confused, I would grab a wiring diagram, as your vehicle may be different. Especially with E39 models, so many wiring configurations. - Nick at Pelican Parts
 

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Page last updated: Fri 12/9/2016 02:05:25 AM