Bought a used (salvaged) 2011 Altima Hybrid 1.5 years ago. It was repaired by an auto shop before I purchased it. Drove it with no problems. Currently only has 50,000 miles on it.

Last month the AC started blowing hot air, blowing cool air for about 1 min, then either blowing hot air again or shutting off. This only happens when the weather is 80 degrees or higher.

Took it to the dealership for a diagnostic and the tech said the issue was due to a leak in my radiator hoses. Had the hoses, reservoir and clamp replaced all at once. The tech and service member assured me there were no more issues with the car and that it was "good to go."

Drove it off the lot, and the AC issues continued. I don't want to take it back to the dealership since their customer service was horrible (never called me back when thy said they would and took 3 weeks to repair my car). I no longer trust them.

Anyone have any experience with this issue or have any insight as to what the cause is? Could it be a compressor issue, temp sensor issue or something else completely?

Thanks for any replies!

I'm guessing you are leaking freon from the AC hoses or connections, and the mechanic simply added more freon without fixing the leak.   Was the AC cold after you left the shop but the AC gradually got warmer?  If so, it sounds like leak to me.   You might consider taking your car to Akins Auto Repair.  They will take care of you:

yelp.com/biz/akins-auto-…

Hi George, thanks for the reply! The AC was cold for maybe 30 seconds - 1 min when I started driving away from the service center. Then it started blowing hot/shutting off again. Thank you for the auto shop suggestion. Unfortunately I'm not in San José at the moment and won't be back for a few weeks. Would like to get it repaired asap, but I'm having a hard time finding a good shop in the city I'm staying in.

Hi George, thanks for the reply! The AC was cold for maybe 30 seconds - 1 min when I started driving away from the service center. Then it started blowing hot/shutting off again. Thank you for the auto shop suggestion. Unfortunately I'm not in San José at the moment and won't be back for a few weeks. Would like to get it repaired asap, but I'm having a hard time finding a good shop in the city I'm staying in.

I would not trust your dealership either.   To the best of my knowledge, the radiator hoses are not related to your air conditioning system.  The radiator hoses contain engine coolant to keep the engine cool.  The air conditioning hoses contain freon to keep the car interior/driver cool.

I just read your post more carefully, if the AC is intermittent, it may not be a leak.

I did some more internet research and apparently one possibility is the radiator fan not working properly. I just drove it to run an errand and now I'm hearing a knocking noise whenever I accelerate. Looks like I'm gonna be needing a lot of repairs done. Sigh. Anyways...thanks for your help George. Much appreciated!

A car has 2 control systems, the AC portion cools the car  the heater portion heats the car.  If both are on you can get an over all hot air car so the dealer may have performed a possible  fix.   Since it is now not working they probably just replaced some hoses and just thought it was fixed.    The car heat exchanger control may be broken and cycles heat on then heat off.  Do you have auto temp control or a manual ( set for 70 deg or set for blue range)     Knocking on acceleration could be just cheap gas. especially on a hot day with the AC on.  But it could be the AC compressor is going bad .

Thanks for the input! Now that I think about it, the knocking started a day after I pumped gas. I hope its the gas and not something more serious

If it is knocking continuously you have a big problem bring it in,  but an occasional knock is generally OK.  It was hot outside last week.

Just to clarify, an AC works by cooling air a certain amount of degrees before it enters the inside of your car.  For example, it will cool the air 30 degrees lower than the current temperature.  Thus, if the outside temperature is 70 degrees, your AC will be output 40 degrees of cool air.  But if the outside temperature is 100 degrees, then you will only get 70 degrees of cool air.   That is why some people think their AC does not work when it is hot outside.