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7 Series - E38 (1995 - 2001)

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  #1  
Old 09-08-2013, 07:58 PM
anniqu anniqu is offline
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Mein Auto: 1997 740i
97 740i AC Fan

I have a 97 740i, As soon as I turn on the car the fan blows on high and the fan speed cannot be controlled by the dash controls. I ran a kill switch from the fuse box in the engine compartment into the cabin and use it to turn the fan on and off. I usually start the car and then turn the switch to on and the fan blows high , only. The fan seems to have a mind of its own as some days the fan will not turn on all , no matter what position the kill switch is at. I have changed the fuse above the glove compartment , but that had no effect. I have had the car for about 8 years and about 5 years ago I had the blower motor replaced. Before I tear the dash apart I was hoping to get some clarity as to what my problem actually is.
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  #2  
Old 09-08-2013, 08:38 PM
Mayorchuck Mayorchuck is offline
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Which fuse is the switch on, 32 or 20? Sounds like the FSU on the blower motor but need more info.
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  #3  
Old 09-08-2013, 08:42 PM
Mayorchuck Mayorchuck is offline
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Culmination of info I did on the subject:



http://forums.bimmerforums.com/forum...wer-motor-info
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  #4  
Old 09-09-2013, 08:19 AM
anniqu anniqu is offline
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Re fuse

HI, Thnaks for the response . The fuse number is 11. I have attache a pic
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  #5  
Old 09-09-2013, 05:24 PM
Mayorchuck Mayorchuck is offline
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I believe thru testing we determined Fuse 11 works the compressor clutch via the IHKA. Fuse 20 also feeds the IHKA to work the other controls. On your car Fuse 81 powers the relay. This would explain why your blower is still acting up. It's still getting power. Also, the relay behind the glove box was found to be different by a member working on a similar issue. His info is here:

http://forums.bimmerforums.com/forum...fying-relay-K4
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  #6  
Old 09-09-2013, 06:18 PM
anniqu anniqu is offline
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Location: Miami Florida
 
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Mein Auto: 1997 740i
re ac fan

Thanks for your comments , but I am still not clear as to what my problem is. It seems that the fan blower itself is working but whatever is supposed to control it is defective. As I stated earlier my problem is
1) initially the fan would start as soon as I started the car and cannot be controlled by the dash controls

2) installed kill switch to turn the fan on and off

3) Now , some days the fan does not work irregardless of the position of the kill switch

4) Other days it is back to working , controlled by the kill switch


Do I have to tear the dash apart and replace the fan or should I be looking elsewhere ??
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  #7  
Old 09-09-2013, 07:03 PM
Mayorchuck Mayorchuck is offline
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What I mean is the the control unit/dash controls/IHKA, whatever you want to call it, is fed by Fuse 11 AND Fuse 20. Even a defective blower or resistor/final stage unit would need power to run. Even though the lights are off on the dash controls, it is still getting juice from fuse 20. This may be sending a signal to the relay, which is still getting power from Fuse 81. This may be quite normal and the resistor on the blower is bad. There are several connectors on the back of the control module. The one Fuse 20 goes to has the blower relay signal as well as the voltage control to the resistor within the same connector. The voltage control is what sets the fan speed.

It is the 26 pin connector on the back of the control panel if you want to pull it out and check to make sure there is no corrosion on the pins. Detailed pin outs are on the link I sent in the earlier thread. I believe it is either the control panel or the resistor on the blower.
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  #8  
Old 09-09-2013, 07:26 PM
Mayorchuck Mayorchuck is offline
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Do you have a multimeter? If it was mine, I would pull the control module out far enough to get to the wires. On the 26 pin connector there is a blue/red wire on pin 8. When the blower control is all the way down, that wire should read .25 volts. All the way up it should read about 7 volts. If it is reading correctly on low and the fan is blowing full speed, the problem is your resistor or blower. If it stays at 7 volts or higher no matter where the controls are set, the problem is with control module.
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  #9  
Old 09-09-2013, 07:29 PM
anniqu anniqu is offline
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re ac fan

THe lights come on , on the control panel when I use the kill switch and and blower runs. Sometimes even if I have the kill switch in the on position , the lights will be on , on the control panel ,but the fan does not work . I will pull it out and check for corrosion
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  #10  
Old 09-09-2013, 07:33 PM
Mayorchuck Mayorchuck is offline
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Also note my second post. We posted around the same time.
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  #11  
Old 09-09-2013, 07:35 PM
Mayorchuck Mayorchuck is offline
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This is how I pull the module if you have not done it before.

http://www.laczik.org/BMW/repair/E38_AC/E38_AC.html
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  #12  
Old 09-13-2013, 09:06 AM
anniqu anniqu is offline
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re ac

Thanks , I will try this on the weekend
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