Intermittent A/C not blowing cold air & the A/C green light flashes on 1994 Toyota Camry

Replaced compressor 1 1/2 yrs. ago, with relay switch. In Aug. A/C began with problem of not blowing cold air & A/C green light on interior switch would flash. This began occurring occasionally, then more frequent, finally A/C stopped blowing cold all the time. Mechanic replaced Pressure Switch & it worked fine for 30 days. Then same problem began all over again. What is wrong with it? Did the car need a Pressure Switch? Cost to repair?

Asked by for the 1994 Toyota Camry
Have the freon charge checked, if low again you have a leak in the system that needs to be fixed! I am sure it was recharged 30 days ago when the switch was replaced. No way to say if it needed that switch or how much the repair cost will be until the problem is found. Let the mechanic check it out.
The freon levels have been checked numerous times - the air is cold when it is working, so it's not a freon problem. He has checked the system numerous times. Was hoping someone may know what causes this type of problem and why it worked for 30 days with a new pressure switch, only to have the same problem reoccur.
Without actually looking at and testing the system, can only guess at it!!
So i did.
1 more answer , 1 more comment
there is an updated a/c relay that may fix the issue,i seen this alot
The Relay Switch was replaced 1 1/2 yrs. ago & my mechanic thoroughly checked it in Sept. when problem began. Is that what you are referring to when you say a/c relay?
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