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Discussion Starter · #1 ·
I have 1997 528 with 144K on it. The AC compressor was making a knocking sound when in use however it did cool the car down.

I think the compressor is shot however the air through the vents cools down when the cars is rolling. If the car is sitting still the air is plain hot.

When rolling It does not cool down as much as a good working AC, yet it is colder. The compressor is making more of a fluttering noise now.

If the prevailing opinion is to replace the Compressor then so be it. However could this also have anything to do with the Aux. fan or the FSU.

Hot as hades in the South!
 

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Two potential problems - 1) bad compressors 2) refrigerant leak

Simple check: hook an R-22 high/low pressure gauge set to the high and low pressure ports. With the motor running, AC on, measure the high and low pressures. For a properly operating system you should see high side pressures around 325 - 375 psig and low side pressures (in a hot car) of 85-100 psig. A unit with a fault compressor will have high side pressure much lower and low side pressure higher than listed above. A unit with a functioning compressor but low charge will have both pressures lower than listed above.

Note: If you are not familiar with refrigeration systems or do not have the specific automotive adaptors for the gauge set, take your car to a professional. Get caught venting R-22 to the atmoshere and the EPA can fine you mucho $$$$$$$.
 

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Suspect auxiliary fan problem

ARJMServices said:
I have 1997 528 with 144K on it. The AC compressor was making a knocking sound when in use however it did cool the car down.

I think the compressor is shot however the air through the vents cools down when the cars is rolling. If the car is sitting still the air is plain hot.

When rolling It does not cool down as much as a good working AC, yet it is colder. The compressor is making more of a fluttering noise now.

If the prevailing opinion is to replace the Compressor then so be it. However could this also have anything to do with the Aux. fan or the FSU.

Hot as hades in the South!
http://bimmerboard.com/forums/posts/221541/

cn
 

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Have your auxiliary cooling fan checked out. It's the electric fan in front of the radiator. See if it runs when the a/c is on. If not, you will need to replace it.
 

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Discussion Starter · #5 ·
The Aux. fan is functioning properly I checked last night using the bmwtips direction.

The Low side pressure is high.

Andy
 
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