problem with house AC, any hvac techs?

[mrb]

house A/C is a split system, 7 or 8 years old Ruud with scroll compressor. When it turns on it blows cold for a minute or two then the air becomes room temperature. Outside, the compressor and condensor fan are running. I felt the lines, and the large one is cold when it first starts up but is not cold anymore after a few min. There is a high pitch squealing noise coming from the compressor, not a mechanical noise, but it sounds like liquid flowing.

any thoughts? could it be stuck expansion valve?

 

[mrb]

update: i went in the attic, the expansion valve was making some funny noises. I noticed one of the capillary tubes from it (the one that goes to the smaller line) had a very sharp bend in it. I straightened that out then the expansion valve started making the normal continuous hiss, but the air still isnt as cold as it was before the problems started.

 

[hydramatic]

suction line should be cold and sweat if it`s humid..sounds like it`s low or restricted

 

[jwillis]

It does sound like it might need freon added. (Or whatever they use now days)........jwillis

 

[oltruckag]

Is the coil frosting over? (or frozen solid?)

Take an amp draw on the compressor and compare it to the data plate on the condenser - see if the compressor is really "working".

 

[bonneyman]

If the unit has been working OK for 7 or 8 years, and is now working only so-so, I'd have to guess a freon restriction issue.
Thermostatic expansion valves typically have a fine screen at the inlet port - to prevent any small particles from entering the valve and making it malfunction. Even if a system is running perfectly, it still wears. Little particles of metal, winding insulation, carbon, ect. are produced. I'd definitely check the expansion valve screen - it might be clogged. That could account for the many years of working, and only now has the screen plugged up enough to reduce the freon flow to a point that the cooling is insufficient (and it could account for the hissing noise.)