Automotive Air Conditioning Information Forum

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?

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.

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

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

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.

New OE Compressor.

14-0170NC

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

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.