I'm new here and am sure there is a thread about this but have searched to no avail, so here goes.

I own a 2007 audi a6 3.2. The ac has been consistently getting warm over the past 6-7 months. I have had the system regassed a couple of times and it works for a little while and the gets hot again. The shop put uv dye in the system last time I had it recharged and then I took the car back in today and they are unable to see where the leak originates.

When I first start my car, the ac it smells musty and then recently had another smell come through the system briefly, almost chemical smelling. I know the cabin filter needs to be replaced.

Because it is difficult to access the evaporator, they are guessing that that is the problem.

When the ac starts becoming warmer it starts with the passenger side vents blowing warm air and then later the driver side is also hot.

There is pressure in the system and the compressor engages fine, do you think that the entire evaporator needs to be changed or possibly another problem?