Usually the expansion valves should not have clogged due to debris if there was a drier in front of the line before freon entering the valves. More commonly, the issue for the valves clogging may be due to moisture in the system. You will notice the air will be cold initially, then gradually warm up, then the system shuts off for 5-10 minutes, then the system will work fine for a while until the valves freezes up due to moisture and air becomes warm again. Basically the system will cycle cold/warm. Find another reputable A/C shop and have them replace the driers and evac the system and then fill with fresh clean freon.

If your system totally stop getting cold and it only blows warm air only, then the valves are clogged and needs to be replaced.

 

Yes, moisture in the system will cause the valves to clog but I have seen many cases from doing A/C work that there can and sometimes will be pieces of debris in the expansion valve. The drier is in the high side of the A/C system but will bypass when it can no longer filter out the moisture, hence, clogging the valves with debris and moisture.

 

Well the other day when i was on the highway it was blowing the tiniest little bit of cold air, just slightly and then went back to blowing room temp air unfortunately. I thought I got lucky or something but when I went back and drove it a few more times it was just blowing room temp air unfortunately.