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BMW E39 Blower Motor Testing
 
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Pelican Technical Article:

BMW E39 Blower Motor Testing

Kerry Jonsson

Time:

4 hours4 hrs

Tab:

$0

Talent:

****

Tools:

Test light, Digital Volt Ohm Meter (DVOM), jumper wires, test light, socket set

Applicable Models:

BMW E39 5-Series (1997-03)

Parts Required:

Blower motor, blower motor, final stage

Hot Tip:

You don't have to remove the dash to test the blower motor

Performance Gain:

Figure out why the blower motor is not working properly

Complementary Modification:

You can now replace the dash pad

The blower motor controls the airflow of either outside or recirculated air. When you push the button on your IHKA control unit for the blower motor speed the IHKA control unit sends out an electrical signal to both a blower motor relay and the blower motor final stage. This electrical signal tells the final stage to either spin the blower motor a lot for maximum air flow or only a little for minimum airflow. If you push the button to change the blower motor speed and nothing happens you may have a blown fuse, a bad blower motor relay or a bad final stage. There have been cases where the final stage has kept the blower motor running while the ignition key is off, therefore draining the battery and leading to a "no-start" problem the next morning. In this tech article we are going to review how to test each component in the system

Here we are at the fuse box.
Figure 1

Here we are at the fuse box. It isPictured here with the glove box removed but you do not have to remove the glove box. One of the first steps in diagnosing a blower motor problem is to verify the fuse is good.

On our 1997 BMW 540 fuse # 28 (green arrow) is the power supply for the blower motor.
Figure 2

On our 1997 BMW 540 fuse # 28 (green arrow) is the power supply for the blower motor. You should unplug the fuse and see if it is blown. You are going to need to look at a wiring diagram for your specific car to make sure you are checking the right fuse. Notice this one has been replaced before as it does not match the other fuses.

Blower Motor Relay Testing: The blower motor relay is mounted in an electrical housing mounted in behind the glove box. To access it you will need to remove the glove box. Follow the procedure for the tech article on glove box removal and then continue with the following steps.
Here we are underneath the dash on the passenger side at the top edge of the carpet.
Figure 3

Here we are underneath the dash on the passenger side at the top edge of the carpet. Remove the 10mm plastic fastener (green arrow). You can see my extension and socket in this photo, the green arrow points to the location of the plastic nut.

Here we are behind the glove box looking up at the ceiling of the inside of the dashboard.
Figure 4

Here we are behind the glove box looking up at the ceiling of the inside of the dashboard. Remove the two 10mm plastic fasteners (green arrow). The second plastic fastener is already removed (yellow arrow)

Pull down the right side of the electrical housing to access the blower motor relay (green arrow).
Figure 5

Pull down the right side of the electrical housing to access the blower motor relay (green arrow). You can unplug the relay and test if from there but it is very difficult because there is little room. It is much easier to access the wiring underneath the relay.

Move the 4 wires that attach to the blower motor relay (now you know which one it is).
Figure 6

Move the 4 wires that attach to the blower motor relay (now you know which one it is). The yellow wire, green tracer (green arrow) is the voltage supply coming out of the relay (pin #87 on the relay) and going to the final stage. This wire should have battery voltage on it when you have the ignition key on and the IHKA control unit on. If it does not you can supply battery voltage through a fused jumper to bypass the relay and see if the blower motor now works.

The red wire, blue tracer (yellow arrow) is the voltage supply into the relay (pin # 30 on the relay) from fuse # 28 mentioned earlier.
Figure 7

The red wire, blue tracer (yellow arrow) is the voltage supply into the relay (pin # 30 on the relay) from fuse # 28 mentioned earlier. Make sure you have battery voltage with the key on. You can use the voltage on this wire to jump voltage to pin #87 to bypass the relay also and see if the blower motor works. Make sure the exposed metal of the jumper wire does not come in contact with ground or you will be creating a short and blowing the blower motor fuse.

The green wire, blue tracer (red arrow) is the relay control (pin # 86) from the IHKA control unit.
Figure 8

The green wire, blue tracer (red arrow) is the relay control (pin # 86) from the IHKA control unit. This wire should have voltage on it when the ignition key is on and the IHKA control unit is also on to activate the relay. You can use a fused jumper to provide power to pin # 86 and you should hear the relay click when activated. While activated you should have power on pin # 87. If you donÂ't you have a bad relay.

The brown wire, black tracer (purple arrow) is the ground for the relay.
Figure 9

The brown wire, black tracer (purple arrow) is the ground for the relay. If the relay is not working you can jump this wire to ground and see if it starts to work. If it starts working then you have a bad ground or this wire is broken somewhere. You can run your own wire and attach it to a good ground to fix that problem. Installation is the reverse of the removal procedures.

Testing the Power Stage: To access the power stage you are going to need to remove it. Follow the procedures in the tech article for blower motor final stage removing, then follow these steps.
With the blower motor final stage unplugged you can see the numbers on the connector.
Figure 10

With the blower motor final stage unplugged you can see the numbers on the connector. Pin # 1 (green arrow) is a black wire, with a green tracer on our 1997 BMW 540. You will have to look at a wiring diagram for your specific car as wire colors can change from year to year. The green / black is the ground for the blower motor. The final stage grounds this wire to get the blower motor to run.

Pin #2 (yellow arrow) is the yellow / green that is the power supply from the blower motor relay.
Figure 11

Pin #2 (yellow arrow) is the yellow / green that is the power supply from the blower motor relay. You should measure battery voltage with the ignition key on and the IHKA control unit.

Pin # 3 (blue arrow) is the smaller blue wire, red tracer that carries the signal from the IHKA control unit to the final stage to command the blower speed.
Figure 12

Pin # 3 (blue arrow) is the smaller blue wire, red tracer that carries the signal from the IHKA control unit to the final stage to command the blower speed. We will discuss testing the voltage signal on this wire later.

Pin # 4 (purple arrow) is the ground for the power stage.
Figure 13

Pin # 4 (purple arrow) is the ground for the power stage. On our 1997 BMW 540 the wire is brown. You will have to look at a wiring diagram for your specific car as wire colors can change from year to year. You can jump this wire to ground and see if it starts to work. If it starts working then you have a bad ground or this wire is broken somewhere. You can run your own wire and attach it to a good ground to fix that problem.

Pin # 5 (red arrow) is a red wire, green tracer.
Figure 14

Pin # 5 (red arrow) is a red wire, green tracer. This is the voltage supply out to the blower motor. This voltage will go up as you increase the fan speed and down as you decrease it. We will discuss testing the voltage signal on this wire later.

You can use two fused jumper wires to bypass the final stage.
Figure 15

You can use two fused jumper wires to bypass the final stage. Jump pin # 1 with #4 (green arrows) and at the same time jump pin # 2 with pin # 5 (yellow arrows). Be careful not to have any exposed metal of the jump wires come in contact with one another. This will cause a short circuit and is unsafe. This is how you can test the blower motor without removing it from the car. The blower motor should run at full speed. If it does not then you have a bad blower motor. 

IHKA Signal to Blower Motor Final Stage Testing:
Attach the red lead of your meter to pin # 3 (the smallest wire), the black lead of your meter to ground and measure voltage.
Figure 16

Attach the red lead of your meter to pin # 3 (the smallest wire), the black lead of your meter to ground and measure voltage. Here we have substituted a yellow test lead extended in place of the d test lead.

Here we are at the IHKA display.
Figure 17

Here we are at the IHKA display. With the ignition key on set the fan speed to the lowest possible setting on and the IHKA control unit. You should only see one bar illuminated.

Your meter should read approximately two volts.
Figure 18

Your meter should read approximately two volts.

Here we are at the IHKA display again.
Figure 19

Here we are at the IHKA display again. Adjust your blower speed about halfway through the range. You should see eight bars lit up on the display.

Your meter should read approximately four point two six volts.
Figure 20

Your meter should read approximately four point two six volts.

Here we are back at the IHKA display.
Figure 21

Here we are back at the IHKA display. Adjust the blower to maximum speed. You should see all the bars lit up on the display.

Your meter should read about eight volts.
Figure 22

Your meter should read about eight volts. The voltage on this wire should go up gradually front two volts to eight volts as you increase the fan speed on the IHKA control unit. If the voltage is changing properly but the blower motor still stays at one speed you have a bad power stage providing the blower motor relay is working properly. If the voltage is not changing like we said then you have a bad IHKA control unit.

Testing the Blower Motor: If you need to test at the blower motor you are going to have to remove the upper dash pad, driver side lower panel and the glove box to access it. Look at tech article on blower motor replacement to access the blower motor for testing.
With the ignition key on and the IHKA control unit on you should have a battery voltage at the blower motor on the red/green wire.
Figure 23

With the ignition key on and the IHKA control unit on you should have a battery voltage at the blower motor on the red/green wire. On our 1997 BMW 540 the wire is red/green. You will have to look at a wiring diagram for your specific car as wire colors can change from year to year. Here we are using a test light to check this.

Here we are at the blower motor assembly under the dashboard cover.
Figure 24

Here we are at the blower motor assembly under the dashboard cover. If you are using a test light instead of a meter connect the ground clip of the meter (red arrow) to the other pin at the blower motor. On our 1997 BMW 540 the wire is black/green. This is the ground control from the final stage. You will have to look at a wiring diagram for your specific car as wire colors can change from year to year.

Here we are at the IHKA display.
Figure 25

Here we are at the IHKA display. Set the blower to maximum speed. You will see all the bars lit up on the display.

Notice how bright the test light is (red arrow).
Figure 26

Notice how bright the test light is (red arrow). If you had your meter connected between these two wires you would see approximately battery voltage.

Here we are back at the IHKA display.
Figure 27

Here we are back at the IHKA display. Set the blower speed about half way. You should see eight bars lit up in the display.

Notice the bulb on our test light getting dimmer (red arrow).
Figure 28

Notice the bulb on our test light getting dimmer (red arrow). This means the power stage is reducing the voltage to the blower motor. If we had our meter connected then we would see below battery voltage.

Here we are back at the IHKA display.
Figure 29

Here we are back at the IHKA display. Set the blower to the minimum speed. You should only see one bar lit up on the display.

Notice the bulb on our test light is barely lit (red arrow).
Figure 30

Notice the bulb on our test light is barely lit (red arrow). This means the voltage is at the minimum level to run the blower motor at a very low speed. If the voltage is changing then the power stage is working properly. If the voltage is not changing then check the power stage. If the blower motor is still not working when you have proper voltage to the motor then you have a bad blower motor.

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Comments and Suggestions:
Bmw M Comments: Hi thanks allot for the details. i have the blower motor running after ignition is off and keys out...can you guide me pls..or i have to go through all those steps described?
Thanks allot
December 5, 2015
  Followup from the Pelican Staff: Use the steps described for testing, if that is the vehicle you are working on. - Nick at Pelican Parts  
b0d Comments: wow ths is exactly what I was looking for and found it on first search, excellent job pelican incredible hope it works
October 27, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Dave Comments: The control head being the climate control display unit? Or is there a different head unit?

Thanks again,

Dave
September 18, 2015
  Followup from the Pelican Staff: Yes, the control panel. - Nick at Pelican Parts  
Dave Comments: Hi. I am having trouble with my 99 E39 wagon. On occasion the HVAC seems to lock on low speed fan as well as the temperature seems fixed. You can adjust and the numbers change and the bars for fan speed change but the fan does not change or the temperature of the air coming out of the ducts does not change. It also will not cycle the ac compressor nor it seems to turn on the rear window defrost. The display has all the lights that indicate things are working. It just doesn't.
September 17, 2015
  Followup from the Pelican Staff: This could be an issue with the control head. I would start by checking the vehicle for fault codes. Then check the output from the control head to the faulty component, for example the blower. - Nick at Pelican Parts  
tomy Comments: Hi I have a 97 535i e39 and am having trouble with the blower speed not working as fast as it used to on full. The code I am getting is;
0 ventalation flap motor
no found 05,26,00,79
Was hoping to find the relay. Is there one thing in particular tp check?
Thanks
August 28, 2015
  Followup from the Pelican Staff: the flap motor fault may be for the fresh air duct motor. I would check with the manufacturer of your scan tool for code definitions on the other faults. They don't show up for me.

We don't have a 535i here in the US that year. But on similar models, the blower relay in located behind the glove box. - Nick at Pelican Parts
 

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