I have 2011 Mazda CX7. When I first turn the car on I can see the A/C clutch being engaged, but after the car runs for bit, then clutch disengages. After a while it starts to engage for few seconds and than back off for about 10-15.
While A/C clutch is engaged, pressure gauge shows it to be on bottom side of green.
I have followed direction on bottle of A/C Pro to fill my unit. But it have not made any difference. It seems that sometimes it decides to start blowing slightly colder air while other times it just blows hot air.
After taking it to Pep Boy's for diagnostics. It turned out to be a relay. Once relay was repaired it turned out that I overcharged the system. Now I taking it to service for evac and recharge. In the end $49 for diagnosis, $60 for evac and recharge, $40 for bottle of A/C pro. In the end I feel lucky to get system repaired for under $200. If I took it to get it diagnosed in the first place it would have cost me whole lot less.
Lesson Learned: Do not charge system unless you have a gauge to read both LOW and HIGH pressure. Next time before I waste money on charging system I will buy the following gauge http://www.harborfreight.com/a-c-manifold-gauge-set-92649.html