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1991 BMW 525i One hair puller

Tiny
FLYBOY97222
  • MEMBER
  • 1991 BMW 525I
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 211,000 MILES
Recently I had a melt-down in my wire harness. After a $2300 repair job I still have no AC.
All the fuses are good, the Mech has replaced several relays.
I was wondering if someone could point me to where I can find a wire diagram of the entire AC unit from switch in the car right up to where it energizes the compressor.
I have no more money to pay a Mech and we still have a heat index of over 100 here in south flordia
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Thursday, October 8th, 2009 AT 3:45 PM

11 Replies

Tiny
FLYBOY97222
  • MEMBER
  • 19 POSTS
Okay have found a diagram and have a something that might be of use to whoever decides to try and help me-

I have narrowed it down to this- after looking at the wire diagram (I can email it to who ever needs to look at it) I wanted to see if I was getting power from the DME to the compressor control relay. So I jumped the #3 to the #5 pin on the relay and whamo I had power to the compressor- BUT still no light on the AC dash control and no cold air.
My question now is this- is it possible to have a bad circuit on the DME in the AC control, and do you think it would be a good idea to buy a DME and try that?
Also according to the diagram I should have a AC compressor control unit in the Left hand kick panel. I removed the panel and there was only a speaker there (I looked behind the speaker and no joy)
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Thursday, October 8th, 2009 AT 6:25 PM
Tiny
FLYBOY97222
  • MEMBER
  • 19 POSTS
So after looking at the diagram again I noticed that it is for a 525i 535i and a M5. I followed the diagram and there is no AC control unit for the 525i only for the M5

I now think since there is a direct line form the DME to the AC compressor Relay that this might be a DME issue.

Any input at all will help
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Thursday, October 8th, 2009 AT 6:48 PM
Tiny
FLYBOY97222
  • MEMBER
  • 19 POSTS


https://www.2carpros.com/forum/automotive_pictures/273641_Screen_shot_20091008_at_75627_PM_1.jpg



https://www.2carpros.com/forum/automotive_pictures/273641_Screen_shot_20091008_at_75652_PM_1.jpg

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Thursday, October 8th, 2009 AT 6:58 PM
Tiny
DOCHAGERTY
  • MECHANIC
  • 9,601 POSTS
Wow. Let me do a bit of research on that and I will see if there is something to be done from this end. Repost with the last 7 of the vin please.
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Friday, October 9th, 2009 AT 12:10 AM
Tiny
FLYBOY97222
  • MEMBER
  • 19 POSTS
BJ66417
1991 525i

DME is a 405
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Friday, October 9th, 2009 AT 4:41 PM
Tiny
DOCHAGERTY
  • MECHANIC
  • 9,601 POSTS
I may be wrong, but the A/C is stand alone on the early production 525. Where was the meltdown and how was it resolved? If you have clutch engagement and no cold air then what are the high and low side pressures? The wiring diagram for your car will be inspected ASAP now that I have the car identified and I will return with an answer no later than Saturday the 10th by 1900 hrs pacific time, ok?
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Friday, October 9th, 2009 AT 9:14 PM
Tiny
FLYBOY97222
  • MEMBER
  • 19 POSTS
No clutch engagement- No lights on the AC button in the car.
I took a jumper and jumped the #3 to the #5 on the compressor relay and got the clutch to engage but no cold air. This leads me to believe that the DME is the problem.
No power to the compressor relay, no power to the pressure switch (hence no cold air)
The 1991 525i uses the DME for the AC on the #85 pin
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Friday, October 9th, 2009 AT 9:36 PM
Tiny
DOCHAGERTY
  • MECHANIC
  • 9,601 POSTS
That is for the idle compensation for when the A/C is on, not for A/C clutch engagement. If there is power at the climate control, then I would begin to suspect the climate control is compromised, perhaps by the trauma you reported on in an earlier posting.
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Saturday, October 10th, 2009 AT 11:24 PM
Tiny
FLYBOY97222
  • MEMBER
  • 19 POSTS
No power to the climate control- I bought a used ECU and it will be here later this week- I'll let you know if that worked.
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Monday, October 12th, 2009 AT 9:41 PM
Tiny
FLYBOY97222
  • MEMBER
  • 19 POSTS
Installed new ECU (DME) and my AC works- thanks for the help
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Thursday, October 15th, 2009 AT 12:23 PM
Tiny
DOCHAGERTY
  • MECHANIC
  • 9,601 POSTS
Thanks for the donation
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Thursday, October 15th, 2009 AT 10:56 PM

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