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AC isn’t blowing cold air after recharge: 10 Causes

Learn the 10 most common reasons why your car isn’t blowing cold air after a recharge

If you’ve recently recharged your car’s AC using a DIY recharge kit and you’re still not getting cold air, there’s obviously something else wrong. I see this complaint a lot. Here are the 10 most common causes of your car not blowing cold air after recharge.

1) You overcharged or undercharged your car’s AC

This is the most common DIY mistake. Too much refrigerant is just as bad as too little. More is not better. With refrigerant R-134a, you only have a 2 oz. window. Overcharging by more than 2 oz actually reduces cooling. Worse yet, you really can’t determine the proper refrigerant charge using only a low-pressure gauge. You need to see high and low pressures, along with ambient temperature and center duct temperature.

See these posts to learn how to test for the correct charge

Heat load test for orifice tube system

Heat load test for expansion valve system

2) Car not blowing cold air after recharge: Refrigerant leak

Refrigerant leak: A leak in the AC system can cause the newly added refrigerant to escape quickly. This is often the primary reason a recharge doesn’t solve the problem.

3. Faulty blend door actuators

The blend door actuators control the temperature of the air coming out of the ducts. If they’re not working properly, they can warm the cold air your AC produces. Always check the operation of the blend doors before suspecting other AC problems.

4) Worn or failed compressor, faulty flow control valve

Compressor failure: If the compressor isn’t working properly, it won’t circulate the refrigerant effectively, even after a recharge. Use a manifold gauge set to read the high and low pressure to determine if the compressor is working properly.

5) The compressor clutch isn’t engaging

You won’t get cold AC if the compressor clutch won’t engage. AC compressor clutch components The compressor clutch is controlled by the AC switch on your heater control, the high and low-pressure switches in your vehicle, a compressor clutch relay, and commands from the computer.

Read these posts to diagnose compressor clutch problems

AC compressor won’t run

AC light flashing

6) Clogged orifice tube

An orifice tube is nothing more than a tube with a filter and a small hole that meters the flow of liquid refrigerant into the evaporator core.

Orifice tubes are color coded. Buy the same color if you replace yours.

The orifice tube in a properly maintained car AC system can last the life of the vehicle. However, if your car AC system develops leaks and you don’t fix them, you set yourself up for total system contamination and orifice tube failure. Here’s how it happens.

Every car AC system has either a receiver drier or an accumulator. These devices contain a packet of desiccant to absorb any moisture that gets into the system. Moisture reacts with the refrigerant and oil to cause acid and foam that can plug the orifice tube and damage the compressor. The desiccant can only absorb a specified amount of moisture. Whenever refrigerant leaks out of your system, ambient air gets in. If you don’t fix the leak, that ambient air and the moisture it carries will eventually cause orifice tube clogging and failure.

The only fix for a clogged orifice tube is replacement, along with a full system flush and a new drier or accumulator.

7) Faulty expansion valve

Some systems use an expansion valve instead of an orifice tube. These are just two different ways to meter liquid refrigerant. Expansion valves offer a

This image shows how an expansion valve AC system works

Click on the image to open full-size PDF in a new window

a slight advantage over orifice tube systems because they’re self-regulating. They detect over-cooling of the evaporator coil and then reduce refrigerant flow to compensate. They usually fail in the full-off mode. But they can also clog, which causes all kinds of weird behavior.

8) Car not blowing cold air after recharge: Clogged condenser

Air must flow freely across the condenser fins to allow the high-pressure refrigerant gas to condense into a high-pressure liquid. If the condenser is clogged with bugs and debris, it can’t cool the refrigerant properly. When that occurs, the high side temperature rises to unacceptable levels, and the high-pressure switch shuts off the compressor.

Also, the refrigerant must flow freely through the tubes in the condenser. Contamination inside the system can clog the very small passages in the condenser, dramatically reducing its ability to cool the refrigerant.