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Discussion Starter · #1 · (Edited)
All, first time posting in roughly 8 years (it's good to be back). This post is more to vent if anything and to see if anyone else has had this problem / bad luck. I recently replaced the a/c compressor and drier on my 1998 M3 sedan. Previously, when the A/C was turned on (compressor clutch engaged), there was a death squeal from the compressor. I thought the compressor was about to go, so I ordered a new Denso unit from FCPEuro. I just did the job this weekend, and took it to my local shop to pull a vacuum / refill with refrigerant.

Unfortunately, the second they turned the compressor on, it's making the same exact death rattle. What are the odds I received a new faulty compressor? Any chance it could be the tensoner for the A/C pulley? The sound is only made when the compressor clutch is engaged, and it sounds like it's coming from the compressor, not where the tensioner is located.

Compounding this, when the shop when to turn on the fan speed through the climate control display, there's no airflow. So either a fuse has gone, or more likely the blower motor resister has died, or possibly the blower motor itself has failed. I'm about to dive into this separate issue. But since I have no airflow, I'm unable to determine if the noisy compressor is even blowing cold air.

Bright side though, at least my a/c system held the vacuum and is holding pressure / refrigerant.

Anyone want to share a similar experience or have any remarks on what could cause this issue? I'm leaning towards first sorting the climate control airflow issue and possibly just replacing the a/c tensioner before ordering another compressor and sending this one back to FCP. Any thoughts are appreciated.

Edit: I just now noticed the A/C belt seems to be slipping - thoughts on the tensioner being bad / incorrect tension? The belt feels tight with not much play.
 

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1984 633CSi, 1985 635CSi, 1985 325e, 1987 325is, 1993 325is, 1995 318is, 1995 M3, 2003 F150
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Welcome back!

It might sound like the squeal is coming from the compressor, but the problem is the tensioner.
 

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The tensioner pivot bearings are not sealed. These can rust with age and lock in position, not provide actual tensioning force.
INA is/was the OE supplier for these parts. Replace the entire tensioner assembly and belt. Non-BMW logoed INA tensioner components are inexpensive.
Probably should look at alternator side as preventative maintenance.


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Discussion Starter · #4 ·
@hornhospital @bluptgm3, thank you both for your replies. I am thinking the tensioner is likely the culprit so appreciate the input. Fun fact, on my 1998 M3 sedan it was already on its (at least) second A/C compressor at 165k miles. The unit I removed was a very grimy Denso compressor with "Made in USA" markings on the back. The new Denso compressor installed is now "Made in Japan", so at some point Denso seems to have shifted production. I previously replaced the very leaky valve cover gasket so hopefully this new compressor remains nice and clean. The drier was the original BMW part, so it seems whoever did the previous A/C work neglected to change it. I also removed both the high and low pressure lines and flushed them / put new O-rings on them.

Will provide an update to the thread once I've replaced the tensioner and fix the blow motor / blow motor resister issue of no air out of the climate control vents. I tested the fuses yesterday and they all tested good, so unfortunately it's not as simple as that. Will first replace the resistor and fingers crossed that fixes the issue.
 
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