Yes, it might be the evaporator and you might be low on refridgerant. However, it might not be as well. My car exibited very similar symptoms, and it was the compressor. I had bought the car used, but knew that the evaporator had been replaced a year earlier. Based upon some of the posts here, I first tried adding refridgerant. Yes, the only correct and I suppose accurate way to make sure that you have the correct amount is to evacuate and refill, but many people with slow leaks seem to be fairly successful with doing occasional refills with a kit. That did not help, and in fact seemed to make things worse (my compressor quit cycling completely).

Bottom line, my compressor was bad. That necessitates a new compressor and new receiver/drier. The orifice tube may or may not be replaced at the same time (it's inexpensive, relative to the rest). That fixed my problem, but not cheap. Dealer wanted $1500. I got it done at Swedish Engineering in Marietta for $870.

Phantom