Low Cooling AC

[kapilamuni]

Hi all,

Recently changed my car's AC compressor clutch bearing. All went week & afterwards cooling was perfect for only 3 days.
Now the cooling has reduced to a very low level.

Here are my observations;
Outside temp = 32 C
When idling @ 750 RPM low = 75 PSI HIGH = 170 PSI, Interior temp = 27 C
1500 RPM LOW = 55 HIGH = 180 Interior temp = 26 C
2000 rpm low = 45 high = 200 Int temp = 25.5 C

With a card board inserted in front of AC fans, to cover air flow

2000 RPM LOW = 45 HIGH = 210 Int temp 24 C

Your advise appreciated.

[kapilamuni]

Oops. Forgot add.
My car is BMW 525TDS with ND 10PA17 compressor.

Also, noted that with AC off, after about few minutes LOW = 120 PSI & HIGH = 120 PSI.

[Tim]

What year?

[kapilamuni]

It's 1996 june.

[Tim]

No listing in the US for that vehicle. If an expansion valve system. Your low side pressures are high.

[kapilamuni]

Yes, it's an expansion valve system. What could be the reason/s to have high low side / low high side pressures?

[Tim]

Is this an original R134a vehicle? Charge levels is a place to start. Possible restriction but unlucky. Normal expansion valve systems will have a low of around 12/18 at high RPM.

[kapilamuni]

Yes it's original system came with the car.
Can it be the clutch not engaging properly? Before this issue, on & off the belt slipping screeches were heard but not continuously. But cooling was not affected. Now it's not making such noises & the belt is fairly new.
The ratio you mention, is it low/high pressures or temp/pressure ratio?

[Cusser]

On some AC clutches, the gap becomes too large and and will not engage; can be reduced by removing a thin shim.

[kapilamuni]

You are head-on.
Removed one of the shims and cooling back to normal.

Thanks.