Rick's Free Auto Repair Advice

Why is my car AC not blowing cold air

Reasons why car AC is not blowing cold air

Here are the top reasons why your car’s AC is not blowing cold air.

Your car’s AC is low on refrigerant

Low refrigerant will cause no cold air, slightly cold air, air that cold for a while and the airflow stops, or rapidly AC compressor clutch cycling.

Your car’s AC is a sealed system. So if it’s low on refrigerant, there’s a leak. Anytime you have a leak in an AC system, you also have air in the system. If you just add refrigerant, the cooling might improve, but it will never cool as well as a system with no air. Air in an AC system reduces cooling.

Air in the system contains moisture. Moisture reacts with the refrigerant and oil to for corrosive acids and sludge which degrades the compressor and clogs the expansion valve or orifice tube.

Adding refrigerant without getting rid of the air is NOT the proper way to fix a car AC not blowing cold air problem. It will also cause long term and very expensive problems

Adding refrigerant from a DIY kit that contains a leak sealer will contaminate your car’s refrigerant. If you ever need to have it evacuated and recharged by a shop, you will have to pay extra to have the contaminated refrigerant/sealer removed and recycled. The sealer damages the shop’s recovery machine and you have to pay for that.

Your car’s AC has moisture in the system

As I mentioned above, when you have a leak, outside air gets in the system and that carries moisture. Moisture can cause the expansion valve to freeze, resulting in periods of cold air followed by warm air. The only way to fix this is to evacuate the system, fix the leak and refill with refrigerant.

Clogged or intermittent expansion valve

As expansion valves wear due to lack of lubrication, H block expansion valve with calloutsthe moving parts can seize temporarily, resulting in periods of cooling, followed by no cooling. Or, the expansion valve can clog due to debris or sludge in the system caused by moisture reacting with the refrigerant and oil. In that case, the only fix is to evacuate the system, flush the lines and replace the expansion valve.

Clogged orifice tube

Sludge and debris can clog the filtering screen in the orifice tube resulting in no cooling in a fully charged system. The only fix is to evacuate the system, flush the lines and replace the clogged orifice tube.

AC orifice tube

New and clogged AC orifice tube. Clogged tube shows evidence of “Black Death.”

Worn AC compressor

The #1 killer of AC compressors is lack of lubrication. If the system has lost refrigerant, it’s also lost some oil. If you just used a recharge kit without adding oil you’ve helped caused the demise of your compressor.

Restricted condenser

AC condensers have very small passages and those passages can get clogged with sludge and debris. The debris comes from rubber hose deterioration, metal compressor fragments and receiver/dryer degradation. The condensers in late model vehicles have passages so small that they can’t be flushed, so the entire condenser must be replaced.

microchannel condenser

Your radiator fans aren’t working properly

That’s right, those fans must operate and maximum performance. If they run, but at a speed that’s too low to cool the condenser, AC pressures will skyrocket and the system will shut down.

How to diagnose your car’s AC system

You’ll need a manifold gauge set, a multimeter, and a temperature probe

Then, start with this post

Or, find your exact symptom here.

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Posted on by Rick Muscoplat

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