The brief
Jey's A7 was blowing warm air from the vents, and warm air doesn't always mean a bad compressor. He brought it in. The aircon is a sealed system, and if it's low on refrigerant the air won't cool no matter how hard the compressor works, because there's nothing in there to carry the heat away. Refrigerant only leaves a sealed system through a leak, and the high-pressure side runs through metal pipes that sit in the engine bay and along the front of the car, where heat cycles, vibration and the odd stone chip eventually crack a pipe or a joint. Once the charge drops far enough the cooling falls away. A leaking pipe doesn't fix itself, and topping the system up just sends fresh gas back out the crack, so the leak has to be found, the pipe replaced, the drier renewed and the system properly recharged.
The diagnosis
A leak check on the aircon traced the loss to a high-pressure pipe, cracked and weeping refrigerant, which is why the system was low and the air warm despite the compressor running fine. The compressor, the condenser and the evaporator were sound otherwise. That's a pipe replacement plus a fresh receiver-drier and a full recharge, not a top-up that would leak straight back out.
The work
The remaining refrigerant was recovered, the cracked high-pressure aircon pipe removed and a new genuine Audi-spec pipe fitted with fresh O-rings, and a new receiver-drier installed since the old one had absorbed moisture. The system was pulled down to a long, deep vacuum to confirm it held and to dry it out, then recharged with the correct weight of refrigerant and the right oil charge. A check at the vents confirmed cold air at idle, holding cold under load, with no leak.
The outcome
Cold air at the vents at idle and on the move, strong cooling, the charge holding, and no leak. The A7 went home with the aircon working properly. Warm air with a healthy compressor is a low system, so finding the leak, replacing the pipe, renewing the drier and recharging it right fixed the cooling for good rather than a top-up that would have leaked away again.
