Outside Compressor gets power, seems to work, but does not cool

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Old 07-29-16, 11:09 AM
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Outside Compressor gets power, seems to work, but does not cool

Hello members, and thank you for the time spend reading and possibly helping.

Our AC stopped cooling air is moving through the ducts, inside fan is circulating the area, outside fan of the condenser unit works, compressor makes noise as if it is working.

Outside unit is Lennox HS26-411-1P, more than 15 years old. Capacitor and contactor were replaced a week ago.
The Compressor is engaging but does not cool the incoming copper coil is warm, but the outgoing is not cold enough. The temperature delta is not it was last week. I can tell the compressor is engaged by the sound and the small vibrations it makes.

Initial issue (couple of weeks ago) was that the outside unit would not run. I replaced the capacitor (old one was dead) and the contactor (the low voltage coil was weak resistance was fluctuating when measured ) with units with identical specs. Unit worked great for 4 days and then the air coming from the vents would not be cold.

There is 24V AC coming from the inside unit.
Everything looks normal when I turn the AC on, external unit gets 24V, the delay TOC works and after 8.5 seconds it engages the contactor. The fan starts and the compressor kicks in. So far all seems/sounds normal.
But it does not cool the coolant enough. The outgoing pipe bringing the coolant to the inside unit (in basement) is just slightly colder and not as cold as usual.
Is there anything in the inside unit (or in the system) which would prevent the Freon to circulate? What else shall I check before the conclusion that I need new compressor (I really hope that is not the case). What would happen if I had a leak? Wouldn't in this case the low pressure switch prevent the control circuit to energize the contactor?
I appreciate any help
 
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Old 07-29-16, 11:51 AM
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While it's possible that your compressor is bad, I think that is unlikely. My guess (I'm not an A/C tech) is that it's one of two things. Either your low on refrigerant (enough there to not trip the low pressure switch, but low enough not to cool properly), or your TXV (thermal expansion valve) is defective (if it uses one, as not all systems use a TXV). My money is on low refrigerant. If that is the case (a competent A/C tech can diagnose that via pressure gauges and temperature readings), you have a leak which must be repaired before more refrigerant is added. This is particularly true because your system, like mine, is old and most certainly uses R22 refrigerant (freon) which is being phased out and is very expensive.

You're likely going to have to get an A/C tech out to look at the system and determine what's wrong.
 
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Old 07-29-16, 12:39 PM
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Maintenance call scheduled

Thanks Bob. I have scheduled a tech to come and check the charge for Monday next week. I will update the results after.
 
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