Did mobile man have a chunky looking machine (proper kit) or a bottle of gas and some gauges?
IME its most unlikely (but not impossible) to be a mechanical faulty and should just require a gas service like this;
- Check for pressure and refrigerant in system.
- Recover and measure amounts of gas & oil remaining.
- Purge air from system.
- Deep vacuum system for a minimum of 30 minutes.
- Vacuum hold to check for minor leaks.
- Replace oil correct for the system.
- Charge with new refrigerant (correct amount for the system).
- Add UV dye to system so any future leaks can be detected and label car with information sticker.
- Run system and check pressures and performance.
- Print out of service information.
More...
Air-conditioning (A/C) system in modern cars is a complex system that requires periodic maintenance. Most often, the system needs topping up using specialist equipment that is used to calculate the necessary quantity to accurately top up the system.
The A/C system on most cars will loose 10-15% refrigerant per year under normal use, more if not used during the winter! We recommend the system is serviced every 2 years to keep it at optimum efficiency.