Now that the summer is approaching I noticed that the A/C does not provide enough cool air on 90 degrees days.

When I noticed the issue I called my local dealer to inquire about A/C service and I was told they charge $295.00 dollars to service the A/C. I thought it was too much and decided to take the RX to a local shop. I explained what was happening and left the vehicle so they could inspect it and waited for a call back. Couple of hours later i received a call, the service man told me that my A/C was low freon (it needed a bottle of R134) but everything looks good. The total charge for this was $104 total.

I picked up the car and drove around but it was not hot enough to notice a change. Yesterday was pretty warm and I had to lower the temp in the control to about 70 degrees that is when I noticed the A/C was not blowing cold enough. Out of curiosity opened the hood with the engine and A/C running and notice the compressor only stays on for about 15 seconds and shuts off for a minute and so on. So decided to change the A/C to manual mode and dropped the temp in the control to the coldest. Still the A/C compressor only runs for about 15 seconds and off for about a minute.

I took it back to the shop where I had the A/C serviced. They kept the car for a whole day and told me that there is nothing wrong with the A/C, they checked the pressure and they said it is full of R134. Of course the day I took the RX to get it looked at for the second time was not hot enough and was told to bring it back when it gets hot.

What do you think about this issue?.
Do I need a new compressor ?
Or maybe a relay a causing it to do this ?