Can I break the lease if the A/C does not work?

You *may* have a defense to the landlord's claim. All leases contain an "implied warranty of habitability," or the requirement that the premises be fit for its intended use; i.e. inhabitation. In the desert, the lack of air conditioning might be consdered to render the apartment uninhabitable, whereas in another state (e.g. NJ), it would not--it would only be an inconvenience.

Where you may have problems are:

1) First, as noted, it must be shown that the lack of A/C rendered the premises effectively uninhabitable.

2) Second, as you note, while the A/C went out 9 times for 1-2 weeks at a time, if it was working as of when you left, that would tend to undercut a claim of uninhabitabilty.

However, even when a condition like this does not rise to the level of justifying termination of the lease, it may still provide a basis for some recovery. This is typically a reduction in rent ("rent abatement") for the period of time (e.g. for nine 1-2 week periods), to reflect the difference in fair market rental value between the rental unit as impaired and an unimpaired unit. For example, it may be that you could be awarded a 25%+ rent abatement for, say 14 weeks. That award could be used as a set off against any amount you may be found to owe the landlord, if your termination of the lease is not found to be justified.

If you can't work matters out with the landlord to your mutual satisfaction and he sues you, you should both raise violation of the implied warranty of habitability as a defense and also interpose a counterclaim against the landlord for the time you were without A/C. Good luck.