Coolant gas seems to be escaping....
Had it re charged yesterday, the mechanic could not detect any leaks anywhere under the hood, seems to think there could be a leak under dash or the tx valve faulty.
Any suggestions?

Be sure .To get to the TX valve behind the dash is a big job and could need a special spanner to disconnect hoses.

Check hoses and Compressor for cracks. The thing behind the dash is a PITA to get too if that becomes the problem and hopefully not.