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Low Side Pressure at Idling Speed

tomibriggs on Sun May 04, 2008 4:44 PM User is offline

Year: 1997
Make: BMW
Model: 528i
Engine Size: i6
Refrigerant Type: 134
Ambient Temp: 74
Pressure Low: 35 - 55
Country of Origin: United States

My compressor had noticable rattle/noise when it cycles on. I added 2oz of PAG oil which I thought would help but didn't do much.

Now my compressor only cycles on after 5 to 10 minutes of driving the engine reaches normal temp. When the car is not motion, the compressor cycles off unless I rev the engine to atleast 2500rpm.

I jumped the compressor to force it to cycle on and get pressure reading from the low side. These are the approx. readings I got:

55psi at 700rpm (normal idle) - air NOT that cool
35psi when I rev the engine to 2500rpm - air IS cool

Does this mean that my compressor is too weak to pull down the low side pressure at idle? Any temporary remedy while I'm saving up for a new compressor & dryer?

Thanks in advance!

Edited: Sun May 04, 2008 at 4:45 PM by tomibriggs

Chick on Sun May 04, 2008 8:48 PM User is offlineView users profile

Did you add anything other than oil? You need both pressures, can't tell much from the low side, could be very low, or overcharged. The rattle could be the compressor, or just the clutch/bearing. Does it make noise with the AC off? You are going to need both high and low pressures though..

-------------------------
Chick
Email: Chick

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Freedoms just another word for nothing left to lose

tomibriggs on Mon May 05, 2008 12:40 AM User is offline

Quote
Originally posted by: Chick
Did you add anything other than oil? You need both pressures, can't tell much from the low side, could be very low, or overcharged. The rattle could be the compressor, or just the clutch/bearing. Does it make noise with the AC off? You are going to need both high and low pressures though..

The oil came in a 3oz can (2oz oil, 1oz 134).

The compressor does not rattle when the AC is off and the clutch in not engaged. Does this mean there is chance I won't have to replace the entire compressor because that good news to my ears and wallet. Here's the link to a video of someone's BMW 5-Series with the same compressor noise as mine. compressor rattle

I will get the readings from both sides.

Thanks so much for your response!

Edited: Mon May 05, 2008 at 1:00 AM by tomibriggs

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