Engine Size: 1.6L
Refrigerant Type: 134A
Ambient Temp: 105
Pressure Low: 80
Pressure High: 325
Ok guys, I'm just about at the end of my rope with my AC.
I thought I might have had an oil overcharge on my civic. I replaced the compressor, dryer, and expansion valve and didn't do the the best job of flushing. The symptoms were High low and high side pressures, rapid fluctuations in the low side and the compressor was slugging when engine RPM came down to idle
Obviously I had crappy cooling as well.
So the second go around I had AMA do my flushing to make sure it was done right. We re-assembled the system (5oz oil, charged to spec). Car was cooling great late last night (40 degree air, 85 degree ambient).
Went to work this morning, didn't run the AC. Going home I turn the AC on and have crappy cooling and I can tell the comp. is slugging, great! I get home, put the gauges on and have 150 psi static and 325/80 with the AC on at idle.
I really don't know where to go from here. I just don't understand how the AC can be great last night and craptastic 18 hours later.
As always, thx for the help
Is the condenser fan working?
Best bet is to bring it by and let us take a peak at it. Could be over charged or have air in the system. Check the hot water shut off valve making sure it is shutting off the flow of hot water to the HVAC case.
It worked well @ 85f ambient, with no solar load. What were the pressures then?
A condensor airflow issue is my first thought - easily tested with a garden hose.
The compressor is not "slugging", but it does have a heavy load. At low speeds the individual cylinder pulses from both the engine & compressor cause some vibration in the drive - and beat the crap out of the only damper in the loop, the belt & tensioner.
150 psi static is normal for 134a @ 111f. Nothing wrong there.
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
1) 325 psi: scroll comp is OK
2) Slugging pulsation: No, that's scroll's one intake per rev. Scrolls require a pressure damping suction gage, e.g., liquid filled or a restrictor valve in line.
3) Comp momentarily off when slowing to idle: Faulty engine idle speed control telling ECM that idle is too slow, therefore the ECM thinks it must disengage comp so driver will not stall in busy intersection.
4) Suction = 40 psi for good cooling: nope! suction reading is wrong-too high.
5) Suction 80 psi: Wrong, it's lower than that, otherwise discharge pressure would be higher or system would have undesirable content (not 100% R-134a).
6) Maybe evap was messed with and sensing bulb is not tight against suction tube, but not likely because cooling OK at 85 ambient.
7) Bad water valve or blend air door: Does not influence suction pressure other that return air temp because reheat is downstream in the evap air flow.
8) Maybe front fan is faulty and needs high speed, not low speed or is connected with backwards polarity (turning wrong direction). Need focus on that fan!
9) Too much oil: not likely from AMA.
10) Until you get a accurate suction reading and louver temp, it's hard to reckon.
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod
Edited: Fri June 25, 2010 at 9:23 PM by ice-n-tropics
Ok, got home and wanted to get accurate info.
Car was cold (at least as cold as a car gets sitting in 115F air)
Static was 150
Pressures while the AC was on was 290/60
Condenser fan was on and turning in the correct direction.
I decided to hit the condenser with some hose water. Pressure dropped instantly to 160/43.
I called Rob @ AMA and had him order me a condenser. I'll add that he told me I should probably replace the cond. when I started this project....
Do all of you agree that it must be the condenser?
Likely condenser or its fan. Others have asked if the condenser fan is working, you may actually have two fans. You didn't respond whether ALL fans were operating. I'd guess fans more likely an issue than condenser.
Yes, all fans are operating properly.
The condenser is clean and the fins are not bent, etc.... I'd say it's getting good airflow.
I'm guessing I'm not getting good refrigerant flow?
I've only had the car a few months so I don't know the history of the AC. I started this whole project because the armature plate was broke off on the compressor.
I had excessive pressure (290/60) after replacing the compressor, expansion valve, and drier. Had evap, etc flushed by AMA so I know those where done right. I put everything back together and still had excessive pressure. The high side line going to the condenser was also excessively hot, cooling was horrible.
I sprayed the condenser with the hose and pressures immediately dropped to 160/43. This lead me to believe the condenser was not getting good refrigerant flow.
I replaced the condenser yesterday. Pulled vacuum for an hour and held vacuum for 30 minutes before I started to recharge. I got one 12oz can it and my pressure were 200/40. I knew these were too high for only having one can in (system call for 22oz), I hit the condenser with the hose again and pressures immediately dropped to 130/20.
The condenser fan is between the condenser and the motor and sucks air through condenser. Common sense tells me this is the correct direction.
At this point I'm assuming there is a blockage in the system somewhere?
Where is a good place to start? I can't imagine it's the drier or the expansion valve as they're both new.
Thanks for the help,
Does not sound like a blockage. If you have an infrared thermometer check the condenser from top to bottom and see if there are any cold spots. How much oil do you have in the system?
Blockage would have more of very high or low pressure. If you were to have a complete blockage no refrigerant would be moving through the system. So you would see a negative on the low or 400 plus on the high. You seem to have higher than normal pressure on both sides! Which tends to lead to a condenser air flow issue. Again I'm just trying to help with the data being provided. We may need to get it in the shop and see what is going on. We would work with you on that since I believe you bought some of the parts from us.
Any chance you have air in the system?
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