What are common AC leak points for a BL Mazda 3 SP25.
 

My sons BL came home from his short 5km from work yesterday with a AC not working (it was Ok on the way to work. . Checks show that system has zero gas in it so something has suddenly broken and failed. If it like most other cars I've had, it will be the condenser or evaporator leak but before I start checking the system it would be useful to know where others with BL Mazda 3 have had AC gas leaks whether self diagnosed or shop diagnosed.Please let me know. I hope it's not the evaporator as that's a tedious dash out job.