I just did my first automotive AC repair, after the compressor in my 2004 Lancer 2.0 ate itself, cracked its casing, and blew all the refrigerant out.
I think I did the repair & recharge correctly-- and the AC is blowing very cold-- but I'm concerned that the operating pressures are not anywhere close to what they are spec'd to be.
(During recharge, I added ~18oz of r134a, per the yellow sticker under the hood.)
At the time, it was 82F in my garage, so I was expecting to end up in the middle of the range (both low- and high-pressure) for the 80F row.... 45psi for low, and about 190psi for the high side. (When referring to this chart, I assumed that the target low readings were for when the clutch was disengaged, and the target high readings were for when the clutch was active.) However, after my recharge the highest low reading I see (right before clutch engages) is 40psi, and the highest reading I ever see for the high side is 150 (right before the clutch disengages.)
Should I be concerned about these low operating pressures, given my starting ambient temperature? This car is 11 years old, and so the computer & pressure switch have about 160K miles on them.
As I said, AC appears to be working very well. The compressor clutch cycles about 12 seconds on, and 12 seconds off. (I'm not sure what's an exceptable duty cycle there. Also I was parked in a garage, not running down the road, air flow through the condenser wasn't exactly real-world. Of course the fans kicked on whenever the clutch engaged.)
Static pressures (with engine off): 80-85 for both high and low sides.
In case anyone has questions about my methodology, this is what I did:
- Remove old compressor, condenser, dryer, and expansion valve
- Flush lines and evaporator with recommended flush solvent
- Installed (all new) compressor, condenser, dryer, and expansion valve, coating all rubber seals with PAG oil
- Added UV dye and 1.75 oz of PAG-46 oil to condenser (compressor came pre-filled with 3 oz, and total required by manufacturer was 4.75) (Mitsubishi originally called for 'SUN PAG-56', but after-market compressor called for PAG-46, so I used the latter)
- Connected hi/low gauge set
- Pulled vacuum to almost -30
psiinches Hg, observed that level held for 1 hour
- Resumed pulling vacuum for 1 additional hour
- Closed off high & low sides, detached vacuum pump, attached 12oz can of r134a (no additives)
- Pierced first 12oz can, allowed yellow line to pressurize.
- Burped yellow line @ the manifold to purge air
- 12oz can+valve+hose weighed 20.7oz at this point
- Opened up low side, allowed vacuum in system to suck in some refrigerant
- Started car, resumed slowly-turning can... compressor clutch engaged for the first time pretty early into this step.
- After first can felt empty, new weight reading was 8.2 (so, 12.5oz discharged from 1st "12oz" can)
- Closed off low side
- Disconnected yellow hose from can's adapter, then connected to different adapter already installed on 2nd can (at this point, I realized I had made a minor mistake, should have moved the first adapter over to the second can without disconnecting the hose. But I compensated for this by burping the yellow line again.)
- Initial weight of second (partial) can+adapter+hose: 15.1oz
- Final weight of second: 9.6 (so, 5.5oz discharged from 2nd "partial" can)
- Total estimated charge: 12.5+5.5=18oz (actually a little less because of burping and final contents of hoses. I think this is OK because the service manual's specifications page gives an acceptable range of "16.93 - 18.34")