Landlord refuses to fix ac unit

[John Rulloda]

Landlord didnt want to fix the ac unit because the previous tenants dog messed up the outer AC unit and the coils are open and in sight. We have been living with it for 4 years and noticed our electric bill has been higher than ever.  He is now selling the house and the buyers have requested it to be fixed as it did not pass inspection. Could I refuse to pay rent due to this? I live in Hemet, Ca where it is desert like heat most of the year but especially summer. Want to deduct rent for this but need to recoup our total deposit. Any info would help.