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Did I do it right?

Geno on Fri May 15, 2009 11:17 AM User is offline

Year: 1997
Make: Subaru
Model: Impreza
Engine Size: 2.2
Refrigerant Type: R134a
Ambient Temp: 71
Pressure Low: 24
Pressure High: 147
Country of Origin: Japan

Hi all,

Amazing forum! I wish I had found this before I started my current project.

I inherited a1997 Subaru, very low mileage, only about 60,000. Air conditioner had probably not been run in years. No cold air at all, compressor would not engage. I put in 24 ounces of refrigerant, possibly overfilling as capacity was 19 to 23 ounces. Low side pressure was then about 20, would drop to 10 when compressor engaged, highside would spike over 300 then immediately dropped down to about 150. I drove it, and heard a loud foghorn noise from under the hood.I thought the expansion valve was defective.

I replaced the expansion valve, receiver dryer, and all of the O-rings. I put in about 2 ounces of PAG 100 oil. I pumped down the system for about 30 minutes, but it would only reach 27 inches of vacuum, and when I listened carefully I heard hissing from the expansion valve. I removed this, found that an O ring had split, reinstalled with new O-rings and evacuated for about 15 minutes. The system held 29 inches of vacuum, after shutting the valves on the gauges pressure gradually drifted down. Pumped down for a few more minutes, and, vacuum drifted down more slowly. I thought there was a slow leak. Recharged with 23 ounces of refrigerant.

Now, with outside temperature about 70°, air blowing from the vents is 46°. With the vehicle idling, compressor will engage for about 38 seconds, then disengage for eight seconds. Pressures listed above are obviously with compressor engaged. There are no more highside pressure spikes when compressor engages.

I'm wondering if I actually pulled moisture into the system while vacuuming down with a split O-ring, and that I did not hold a vacuum long enough to boil out all this moisture.

So my question is, do I leave it alone, reevacuate and pull a vacuum for a longer period, change the receiver drier or even change the oil. if I need to change the oil, I'd need guidance as to how to remove the old oil.

Any thoughts would be appreciated. Thank you very much.

Thanks and God bless


Chick on Fri May 15, 2009 5:33 PM User is offlineView users profile

You have to have the exact amount of refrigerant in the system, and 71 degrees isn't that warm to really get a good pressure reading, but you are close. It would appear you're a little low, but if you still lost vacuum, you may still have a leak. Now that it is charged, if you have dye in the system, use a UV dye light to try to find it. Condenser leaks is what I find on those mostly.. If no dye, use an electronic leak detector.. But find it, because you can ruin the compressor running it low on charge.. Once you find and fix it, vacuum it down and recharge and make sure you get the right amount in there.. Take into consideration that some is in the manifold set, around three to four ounces depending on hose length.. You have to adjust for that. Look for a high side pressure about 2.2 to 2.5 times ambient when over 75 degrees..Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

Geno on Sun May 17, 2009 7:55 AM User is offline

Hi Chick,

Thanks so much for the reply. If there is a leak, I can't find. I did use a UV light, at night in just about total darkness, and couldn't find anything. The system seems to be cycling more than it should, when driving on the highway at about 60 mph, 80 degree outside temp, the air from the vent will be very cold for about one minute, then warm up somewhat for 30 seconds, then go back to being cold for another minute.

Two questions. First, I'm wondering whether I did not vacuum long enough, and there was still moisture in the system, and the reason that it wouldn't hold vacuum was because the moisture was boiling off. I will install another new receiver dryer, and do a very thorough vacuuming, and see if it will hold vacuum. Anything else to do while the system is empty?

Second, anything special to look for if the system still cycles? Sensor, clutch, etc?

Again, thanks so much for this site, and for the time you spent answering.

Thanks and God bless


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