Volkswagen Repair: A/C Problem in 2000 VW JETTA GLS, thermal expansion valve, vw jetta gls

Question
I recently bought 2000 VW JETTA GLS. The car condition is good but the only problem is with A/AC. When we are travelling on Highways it is working fine. But in City traffic it is giving problem. When we are pressing the accelerator A/AC is working very well, If we released the accelerator ac is not working. even if the car is in parking and if we are pressing accelerator ac is working (i.e. when we are raising accelerator the compressor is working.) One mechanic has seen this car and he is saying that the freon content is fine and there may be problem in Pressure regulator. Can you analyze where exactly the problem exists and please guess and tell me how much money I have to spent to fix this problem. Please help me to get rid of this problem.

Answer
Hi there Kumar;  I would say that the level of refrigerant...134a, is NOT fine.  The only way to know for sure is to connect a manifold gauge set to the system, let it operate, and read the pressures.  If they are normal, then the system is full, but I suspect yours is a little low.  I don't know what part is the "pressure regulator."  However, there is a "thermal expansion valve" that is used for the refrigerant to flow through to enter the evaporator unit...which is where the cooling takes place.  Thermal expansion valves are normally VERY reliable, and very robust units.  But, they too can fail.  I would take the car to another air conditioner shop, and just get a second opinion.  Good luck.