Rick's Free Auto Repair Advice

AC not working – car or truck

Diagnose and fix AC not working problem in your car or truck

When you encounter an ac not working issue, most drivers automatically think their ac system is low on refrigerant. It may be low, but there are other things that can cause ac problems. This article is a summary of several specific articles on how to diagnose and fix an ac not working problem.

I’ll assume the blower motor is working and you’re getting good airflow through the ducts. If not, that’s a completely separate issue from the ac portion of your vehicle. To troubleshoot blower motor not working issues, read these posts.

Start by checking the ac compressor

With the vehicle running, turn the ac to max and blower to high speed.

Air conditioning compressor and clutch assembly

Air conditioning compressor and clutch assembly

Pop the hood and locate the ac compressor. Visually inspect the ac compressor to see if the clutch has engaged and the compressor is rotating. If it’s not rotating, read this post to diagnose the underlying problem

Compressor runs, but air is warm

Don’t rush to judgement on this—it may be caused by a refrigerant issue. But it can also be caused by a malfunctioning blend door that’s adding heat from the heater core to your chilled air. Or, your vehicle may have a heater control valve that’s running hot coolant into the heater core when it should be turned off.

If you get colder air when the vehicle is at idle, but the air

blend door actuator

Check blend door actuator movement

warms up when you’re at higher speeds, you probably have a bum heater control valve or bad blend door actuator. Read this post to learn how to diagnose a bad heater control valve. Read this post to diagnose a bad blend door actuator.

Next, check for proper airflow across the condenser coil. It’s the mini-radiator located in front of your engine radiator. If it’s plugged with insects, dust and dirt, it can’t properly cool and condense refrigerant vapor back into a liquid. If it’s clean and unobstructed, check the radiator fans.

Most late model cars and trucks have two radiator fans and many of those are multi-speed units. So it’s not enough to notice that they’re running, they must run at full speed to adequately cool the refrigerant in the condenser coil. Read these posts to check out the radiator fan situation.

Bad or missing fan shrouds and seals can cause ac not working problems

If you’ve had any front end body work done or had a radiator replaced and the technician didn’t properly replace the radiator fan shrouds and seals, that can cause ac blows warm air situation.

Bad TMX valve or orifice tube can cause ac not working problems

You’ll need a digital meter with temperature probes to diagnose the TMX and orifice tube functioning. Read these posts to learn how to conduct the tests.

Test TMX system

Test orifice tube system

©, 2016 Rick Muscoplat

 

 

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