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Intermittent AC problem - doesn't work when the engine is cold?

samadams4samadams4 Posts: 2
edited July 2016 in Subaru
I have 2007 Subaru Impreza SOHC with manual AC.

The symptom is that the AC works intermittently, seemingly only works when the atmosphere temp is higher, say 90F+, or only when the engine is really warmed up. It does not work first in the morning or cooler evenings. This seems opposite of the most AC symptoms out there online communities.

What was done before this symptom was that the high pressure discharge hose had a leak, and I replaced with the new OEM hose, replaced the receiver drier, added 2ml PAG mid viscosity oil. I used the manifold gauge and the vacuum pump from Autozone and did the evacuation procedure, and the system holds vacuum fine, no pressure loss for 20 min after the pump is turned off.

So, I went ahead and charged the system with R-134 (Factory spec 16 to 19 oz). I actually measured the weight of the can during the charge so I'd stop at about 17 or 18 oz of freon in the system, excluding the small amount I bled out of the manifold before opening the manifold gauge ports.

Everything went well and the air was cold. The pressure read about 25 psi low side, 205 psi high side, 77°F ambient temperature. (Factory spec: 18 - 28 psi low side, 213 - 242 psi high side, with 85°F ambient) As I've done this before successfully, I thought the problem was fixed.

But next morning the AC didn't turn on immediately. What I observed was the AC turns on after driving for 10 min or so, (like it has to be warm enough that the radiator fan turns on by itself before the ac blows cold air). Once it works it blows at about 65°F.

What's causing this and what's the fix? Not enough evacuation? Faulty expansion valve? Not enough or too much freon?

Comments

  • samadams4samadams4 Posts: 2
    Correction. The AC air temperature (when the compressor is engaged) is more like 45F, not 65.
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