I've noticed recently in my 2002 WRX that when I press the A/C button, the compressor sometimes does not come on at all. Other times it comes on, but only for about 10 seconds, then shuts off. I thought this was an issue so I took it to a shop this morning. They just called saying this is normal operation and that the compressor shuts off when it hits its intended pressure. I appreciate them not ripping me off and making unnecessary repairs, but it seems that something is wrong if the compressor doesn't even kick on at all sometimes. I remember in past winters using A/C on "hot" quite a bit to help de-fog the interior windows, so they don't steam up. This doesn't seem right that I can't have the A/C running now. Thoughts?