2004 Subaru Forester rattling noise when compressor is running

[Apache23]

Just did an evac, vacuum pull and refill on a 2004 Subaru Forester. Pressures are good, with the low side at 43 psi and 205 on high side at 82 degrees ambient temp. Blows nice and cold air. I replaced the clutch bearing and inspected everything in the compressor, and found some hairline cracks in the insulated? part of the coil. Will attach a pic. Will this cause problems, and if so, could it be what is causing the "rattling" noise when the compressor runs? The noise was there before I replaced the clutch bearing. The rattling noise sounds like if someone was shaking a plastic PCV valve really fast. That's about the best I can describe it. Any ideas to what is causing the noise?

Hairline cracks in coil

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[JohnHere]

I think the rotary-vane style compressor is on its way out, which is why it's making a rattling noise. In addition, looks like the potting compound sealing the clutch coil is cracking and compromised due to age and/or heat. I'd replace the compressor assembly with a new one (not rebuilt) before it disintegrates internally, which will cause additional problems and expense to repair.

Check with Tim at ACKits.com, this Forum's sponsor, for the appropriate parts.

At 43 PSI on the low side, I'm surprised that you have any cool air at all.

[Apache23]

So is the 43 psi too high or low? I was going by this and a few other charts.

AC pressure chart.jpg (134.78 KiB) Viewed 8701 times

[JohnHere]

For a vehicle with front A/C only, a low side of 43 PSI is too high and corresponds to an evaporator temperature of nearly 50°F, which would yield a center-vent air temperature in the low 50°F to the mid 50°F range, insufficient IMHO to cool the interior on a hot day.

On the other hand, a low-side reading of, say, 30 PSI corresponds to an evaporator temperature of about 34°F, which would yield a center-vent air temperature in the high 30°F to low 40°F range, which is more in line with the cooling you'd expect.

Pressure/Temperature charts can be useful for theoretical purposes in the classroom. But in actuality, the charts can be misleading when compared to the actual working pressures of a correctly operating MVAC system.

[Tim]

New OE Compressor.

14-0170NC

[Apache23]

About to go check vent temp now. Seems like it was very cold, but I'll see.

[Apache23]

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[JohnHere]

Something doesn't add up. With a low side reading of 43 PSI, it's impossible for the center-vent air temperature to be 34.1°F because the evaporator already is considerably above that temperature.

I'll venture a guess that the pros on this Forum don't use an infrared "gun" to measure air temperature and instead use either an analog or digital thermometer with a stem protruding out the back that can be directly inserted into the air vent. It might be possible that you're receiving a false air-temperature reading by using a gun.