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AC is blowing hot air... diagnose?

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Old 06-14-2018, 12:18 PM
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ls2kev
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Default AC is blowing hot air... diagnose?

So every Google search result basically says to recharge with AC Pro... but one result warned not to use this unless you actually know you have a leak (because putting something like that in your system that is designed to clog leaks can damage your car if you don't actually have a leak).

Without getting raped by a dealer, how can I tell if my AC is blowing hot air because I need a recharge?

What other issues could it likely be, and how can I find out?

Thanks in advance for your help!

FYI: This is a constant warm air problem, not intermittently.

Last edited by ls2kev; 06-14-2018 at 12:35 PM.
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Old 06-14-2018, 12:52 PM
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Shaolin Crane
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First would be to check if the compressor is running
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Old 06-14-2018, 01:16 PM
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ben z
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Several reasons why this could be happening other than a leak. Diagnosing requires test equipment and knowledge. To avoid being raped by a dealer, I would get recommendations of a trustworthy indie. It's a Chevy, the A/C system is pretty much generic GM.
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Old 06-14-2018, 01:32 PM
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stingray71
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You don't need a recharge unless you have a leak. They will need to check the pressure to see how much is there and then (most likely) do a leak check to find the component that is leaking. Repair cost will depend on the failed part such as compressor or condenser.
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Old 06-21-2018, 05:42 AM
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Originally Posted by stingray71 View Post
You don't need a recharge unless you have a leak. They will need to check the pressure to see how much is there and then (most likely) do a leak check to find the component that is leaking. Repair cost will depend on the failed part such as compressor or condenser.
Goodyear stores are having a special - Check AC for $9.95
I got mine checked since it's been hot air only. They said it has NO Freon left in the system. It's either all burnt out or leaked. To find the leak, they have to fill it with NEW freon with dye that will show where the leak is. That's a $150 job. Finally, once the leak is determined, then the repair of that part will be another issue. The tech told me, since the car has low miles (35K), compressor & condenser are most likely not the problems, but the valves in the line - those are more prone to leaks.

I am having the AC checked out at another shop next week....we'll see what happens!
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Old 06-21-2018, 06:42 AM
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Originally Posted by Vette_Fan View Post
Goodyear stores are having a special - Check AC for $9.95
I got mine checked since it's been hot air only. They said it has NO Freon left in the system. It's either all burnt out or leaked. To find the leak, they have to fill it with NEW freon with dye that will show where the leak is. That's a $150 job. Finally, once the leak is determined, then the repair of that part will be another issue. The tech told me, since the car has low miles (35K), compressor & condenser are most likely not the problems, but the valves in the line - those are more prone to leaks.

I am having the AC checked out at another shop next week....we'll see what happens!
Maybe I'm old school but I never heard of Freon being "burnt out". I thought AC units were a sealed system and the only way to be low on Freon or no Freon is if you have a leak?
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Old 06-21-2018, 07:28 AM
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Originally Posted by NDMIKE88 View Post
Maybe I'm old school but I never heard of Freon being "burnt out". I thought AC units were a sealed system and the only way to be low on Freon or no Freon is if you have a leak?
True that. One of the guys said, "it depends on how much AC is being used, in some parts of the country AC gets used more than other areas." I'm not sure what he meant or what it has to do with Freon? Does using AC more often use up the Freon more than cars that rarely use AC? Not sure...

I think it's a leak too. Going to another shop to get the Freon FILLED with DYE to check the leak. Only then we'll know the actual location of the leak.
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Old 06-21-2018, 07:42 AM
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Freon being burnt.
Freon contaminated by burnt refrigerant oil, and metal after compressor burns out.
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Old 06-21-2018, 08:20 AM
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Originally Posted by HK770 View Post
Freon being burnt.
Freon contaminated by burnt refrigerant oil, and metal after compressor burns out.
What are you saying - the compressor can be burnt out?

Hope not...
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Old 06-21-2018, 08:57 AM
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One thing to check is the A/C fan belt for looseness or slippage.
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Old 06-21-2018, 09:18 AM
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One issue's not been mentioned a possibility, also.
IF system checks-out w/ no leak(s) might very well be AC's working.
If so there're 'curtains' directing air, it quit remaining closed instead of opening.
When this happens there's no air flow hot or cold.

Repairing this is a genuine PITA fixing curtains/doors.
Dash must comes out for access to components for proper repair/replacement, then parts.
Beaucoup labor hours, naturally.

Let's hope it's only a leak.
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Old 06-21-2018, 10:35 AM
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corvette312
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Three things for hot air: 1) Leak 2) compressor 3) switch
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Old 06-21-2018, 11:58 AM
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Dutch08
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Originally Posted by corvette312 View Post
Three things for hot air: 1) Leak 2) compressor 3) switch
One of those "Recharge kits" at the autoparts store. READ THE DIRECTIONS CAREFULLY, but basically 1) Turn on the AC (switch) 2) Check/Confirm the Compressor is running (Compressor) 3) Add the refrigerant/seal re-conditioner (Not the clogger type) to the AC (small leak) using the supplied pressure gauge.

This worked for my Toyota.

Last edited by Dutch08; 06-21-2018 at 12:01 PM.
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Old 06-21-2018, 12:21 PM
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Originally Posted by Shaolin Crane View Post
First would be to check if the compressor is running
^ this is the proper first step. If it comes on you might have an issue in the heater matrix behind the dash that is preventing the cold air from getting to the correct vent(s).

More than likely the system has no/low pressure or, there is an issue between the A/C compressor and the A/C head unit (fuse, relay, etc)

You can rent a set of A/C manifold gauges from most parts stores that rent tools to check system pressure. I know Autozone rents them out. With these you can check your system pressure both high and low sides and if your system has any pressure at all. There are many good videos on Youtube on how to do this. Once you understand the procedure it takes just a minute to do.

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Old 06-21-2018, 12:25 PM
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And if you do recharge your system NEVER, EVER, EVER put anything in the system other than pure Freon (R134a in the case of the C6) or, pure Freon containing dye. NEVER use ANY freon with any stop leak additive! It can wreak havoc on your A/C system (particularly the compressor, evaporator and orifice tube) and, the recovery equipment used when if/when the system is ever evacuated for component replacement. That stuff can kill an evacuator machine, literally causing thousands of dollars in damage to the shop's equipment.
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Old 06-21-2018, 12:52 PM
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Originally Posted by VtVette View Post
^ this is the proper first step. If it comes on you might have an issue in the heater matrix behind the dash that is preventing the cold air from getting to the correct vent(s).

More than likely the system has no/low pressure or, there is an issue between the A/C compressor and the A/C head unit (fuse, relay, etc)

You can rent a set of A/C manifold gauges from most parts stores that rent tools to check system pressure. I know Autozone rents them out. With these you can check your system pressure both high and low sides and if your system has any pressure at all. There are many good videos on Youtube on how to do this. Once you understand the procedure it takes just a minute to do.
If the system is actually cooling, you will see sweating on the pipes under the hood and one will be cold to the touch.
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Old 06-21-2018, 12:54 PM
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Shaolin Crane
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Most stop leak isn't really "stop leak" any more. Just a different velocity oil that treats o rings which typically cause the small leaks. Even older stop leaks would mever go as far ss the damage described because it would never make it past the orifice tube, rendering the system useless anyways
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Old 06-21-2018, 01:05 PM
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If you don't know anything about how system works take to AC specialty mechanic. Some of the information offered and/or suggested is not credible. Could be many causes. It is not going to be diagnosed on this forum.
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Old 06-21-2018, 01:24 PM
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Originally Posted by Shaolin Crane View Post
Most stop leak isn't really "stop leak" any more. Just a different velocity oil that treats o rings which typically cause the small leaks. Even older stop leaks would mever go as far ss the damage described because it would never make it past the orifice tube, rendering the system useless anyways
A good friend of mine works at the premier auto A/C repair shop here in Vegas. They have spent thousands of dollars tearing down and rebuilding their equipment damaged by A/C stop leak. The stop leak would crystallize inside the recovery machine when a system containing stop leak was recovered then exposed to any moisture. Maybe something has changed but this was an on-going problem for them.
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Old 06-21-2018, 01:29 PM
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Step one is to make sure that the compressor clutch kicks in once you turn the A/C on.

Step two is to get gauges on the low and high side, and check for your pressures. The system has a high pressure switch, and if the pressure gets too high in the system as the Freon heats up, it will kick the system off so you don't blow a line.
Note a orifice tube filter is will show up on the pressure test, with the high to low pressure way out of the norm.

Now the ugly one, and that if the system has a leak. Hence if the system did a full leak out with no pressure in the system, it gets nasty real quick, since this induces moisture to the system, that can not only case rust in the system/parts, but clog the orifice tube filter as well. So even finding the leak to begin with to correct it, doing a vacuum draw on the system to pull all the moisture out of the system, you can still have rust in the system, and/or a clogged orifice tube filter as well.


So on a system that you find way, way low on Freon, then the run down becomes to find the source of the leak to begin with to correct it, pull the system apart to check for rust/clean the system and change the orifice tube filter out if needed, vacuum the system to boil out any water in the system, then recharge the system with fresh Freon and oil.
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