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After looking here A/C not keeping up and also here Air Conditioner Can't Keep up .

I have decided to ask a question that perhaps someone can provide me with more insight.

My AC unit was doing just fine keeping up, until one after noon I had turned the unit to off unintentionally and then back on (kind of quickly - because as I said it was unintentional that I turned it off). Since that time the unit has had a hard time keeping up. I mean I noticed it from the time I turned the thing back on it did not shut off but kept running and the temp in the house was not dropping.

I have a 3 ton R-22 unit (36,000 BTU), the normal pressure readings on the nameplate are 74 for the low side and 244 for the high side. The house is 1300 SQ FT with normal 8' ceilings.

The reading on the low side was 74 PSI and the reading on the high side was 205 at an ambient temperate of about 90 degrees. I am not sure what this is telling me - my indoor temp was at 75 degrees - I have not taken a thermometer to the duct work above the evaporator coil or the vents. Coils are not perfectly clean as in like-new; but they are clean (and I would not suspect everything fine and then because I switched off and then on - suddenly they are an issue.) My filter is clean, I changed the old one out at the time this started because I had new ones and said what the heck it will not hurt it.

Both the evaporator and the condenser fans are running fine.

So, I am wondering "what has changed to cause this issue?"

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  • Usually, short cycling the AC only causes it to wait 5 minutes to restart. After that nothing has changed. Since it is R-22 it is an older unit and may need additional refrigerant added. You should call a reputable HVAC contractor to service it. This is not normally a DIY project but if you take some courses at your local community college you could get a card to buy R-22 refrigerant. Good luck!
    – ArchonOSX
    Jul 29, 2017 at 9:56
  • @ArchonOSX with a pressure reading of 74 on the suction side matching the nameplate - it has proper refrigerant charge. You don't need to take courses - you simply need to pass the 608 certification exam (@$20 the first time) in order to be certified just for the privilege to be allowed to buy R-22.Obviously for that reason a DIY'er would be hard pressed to buy R-22. So why is my high pressure running lower than the faceplate design pressure and the suction is running at design. I don't have a heatpump - typically they have a short cycle protection - but I am not sure on a regular AC.
    – Ken
    Jul 30, 2017 at 0:22
  • I have a 30 year old air conditioner that uses R-22, and it can't be short cycled. It has a 5 minute delay. Passing the 608 without some training would be low probability unless you spent a fair amount of time studying for it. Possibly your compressor is wearing out since it cannot generate the higher pressure with a proper charge. Good luck!
    – ArchonOSX
    Jul 30, 2017 at 10:11
  • @ArchonOSX - I have found a website that has explained it. It could be the compressor piston wear, valve wear, they also mention the expansion - TXV - given the age of the unit and the fact that it is low by about 10PSI for the given temperature - it is probably the compressor wearing. I know I can perform a load test on the compressor to see how much current it is drawing to determine its status. I know enough about AC to be dangerous, but don't work on them enough to be any kind of expert.
    – Ken
    Jul 31, 2017 at 22:35

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