AC blows hot air

My ac unit occasionally blows hot air. I know it’s losing refrigerant, I just don’t know where.
Any suggestions on where to start?

I should add, sometimes it’s slow to blow cold and other times it blows hot after it was blowing freezing cold. Dealership added refrigerant And it seemed to be fine for about 1 month. When issue of blowing hot air again (intermittently) returned I took it to a mechanic I trust. He said refrigerant was low, but could not find the leak outside of pulling the dash, which I didnt have time for. But I’m ready to leave it now until it’s fixed.

You don’t need to remove the dash to find an AC leak.

Anybody who works on AC systems has a refrigerant sniffer.

If they don’t have one, take the vehicle to someone who does.


Thanks, I’ll check it out, but bet he does.

How old is the car and what’s the mileage?

@Tester is correct.

2011 Nissan Cube

sounds like it could be a bad ac pressure switch. if the switch is reading incorrectly it could be turning off ur ac compressor

Thanks so much. I’ll ask Carlos about it.

A 9 year old car. Does not surprise me to be low on refrigerant. While compressors come sealed, over many years the main seal will eventually wear and over time lose refrigerant. This can be a very, very slow process over weeks or months.

I would ask your mechanic to top it off and while doing so add some dye. The dye should show where the leak is. Once he did this have him show you what to check for on a regular basis. The dye will be visible, especially under a UV light.

Forget this under the dash thing… that would be extremely unlikely.

The dye thing he did when he topped it off last month. Thanks for that tip as well.

Your car has a problem with the HVAC blend door actuator or the compressor is disengaging. If the system is low on refrigerant the A/C will blow warm, not cold and hot.

When you take the vehicle to the shop, make sure that they understand that the problem is intermittent so that they check the vehicle over a longer period of time to spot the problem.

It blows, freezing cold then hot air. Sometimes when i start the car it blows warm air, but after a minute will work fine. Usually it works great but starts blowing warm and now the warm blowing will last longer, rather than switching back to cold

Initially we thought it was simple low on freon so we took it to a Nissan dealer who added freon. A month later it was intermittently blowing warm again. So i took it to Carlos at Floyds on Blalock, (my family uses him & I’m new to Houston). Carlos said it was low on freon. Since we had just added freon a month before, he filled it again and added dye.

After that the problem contined. Carlos kept the car for a day but could never get it to blow warm.
I picked the car up. The next week the periods of blowing warm were much longer. On Tuesday i was in the car off and own all day. It was NOT working most of the day. On Thursday I took it to Carlos, a 45 minute ride from my house and it blew freezing cold the whole trip. I was hoping it was finally broke so he could figure it out.
He’s checking various things now.

Thanks for your help.

Sorry for all the bad spelling and wrong words. I was typing from my phone. But I think you can still understand what I was trying to say.


Can anyone recommend an AC repair mechanic?