Rick's Free Auto Repair Advice

Recharged car AC not blowing cold

Added Freon but get warm air

So you bought a can of DIY car AC recharge and added freon but get warm air. I see this complaint a lot. You bought a DIY car AC recharge kit and added refrigerant according to the instructions, but the AC not blowing cold. Here are some of the possibilities.

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 definitely not better.

See these posts to learn how to test for correct charge

Heat load test for orifice tube system

Heat load test for expansion valve system

The compressor clutch isn’t engaging

If the compressor clutch won’t engage, you won’t get cold AC. AC compressor clutch componentsThe compressor clutch is controlled by the AC switch on your heater control, the high and low pressure safety 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

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 tube

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. But 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.

Faulty expansion valve

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

TMX AC system

Click on image to open full size PDF in new window

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.

See these other posts

AC blows warm air

AC compressor oil

AC compressor won’t run

AC light flashing

Car AC compressor

AC compressor clutch

Fix Car AC

Heat load test

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