Car AC Not Blowing Cold Enough

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image of car airconditioning compressor
Air-conditioning Compressor

I get a lot of questions about car air conditioning systems not enough. Especially during hot humid summer days. Most people would like to see frigid air blasting from their small dash vents instantly upon request.

Now that this page is getting some heavy traffic I am adding some additional information and a new “Simple Fixes” video at the bottom along with some related tools and equipment for people who want to take it to the next level. So lets get that cold air back. If we get lucky it won’t be one of the three worst car air conditioning problems on older cars.

Remember, when your cars bake in the sun, for even a short time, the heat stores up in large quantities. You must remove this before it starts to feel cool inside. But what if the air doesn’t seem to get cold after 5 minutes? Unfortunately, a variety of factors affect the actual output temperature at the dash vents.

To follow you’ll find a few examples of common problems that I often discover when inspecting a car air conditioning system not performing as well as it should be. Without a doubt the most common problem that I find is an incorrect Freon charge. The amount of Freon in the system is extremely critical. The manufacturer installs the exact amount that is required for the system to perform at its peak.

GM Car AC compressor
GM Car AC compressor

This exact charge is so critical it is documented in the vehicle’s engine compartment down to the ounce. A few ounces short of a full charge can result in inadequate cooling under high heat loads due to lack of reserve refrigerant.

A telltale sign of this condition would be for a compressor clutch to cycle on and off faster than usual. The rapid clicking sound generated from this condition can usually be heard from inside the vehicle.

Sometimes when people try to recharge a system on their own they fill it with an AC stop leak product. To much of this stuff can make things worse. In other cases people actually overcharge the system which can cause poor cooling performance just as much as low Freon levels. In extreme examples an overcharge of refrigerant can even cause AC compressor damage and noisy operation.

Loss of AC Efficiency

image of car ac condensor
Car AC Condenser

Not as common as the Freon issue mentioned above, but one common in my area at this time of the year is a radiator or a condenser considerably clogged with bugs, dust and dirt, or road debris and trash.

When this junk starts to reduce the airflow that passes through the radiator and then through the condenser it can cause higher than normal high-pressure readings. This in turn can knock several degrees off of the output temperature in the cabin.

This is the kind of problem that slowly gets worse over time. It is very rare that people will take the time to check or clean the radiator and condenser. The fleet company I work for has made this operation part of the scheduled service operations. We have a pressure washer and we physically clean the radiator and condenser fins every 20,000 miles.

AC test guages picture
AC Test Gauges

Although there are lots of other problems that can cause poor cooling the two mentioned above are ones that I find often. If you think your car air conditioning is not blowing cold enough the first step is to check the output temperature at the center duct with a thermometer. I made a video showing how to run an AC performance test.

Make sure the re-circulation or max air mode is selected and the blower is on low speed. 40 – 50 degrees is perfect. On hot humid days in south Florida 55 degrees is welcomed. Step 2 is to have a professional connect a manifold gauge set and get high and low side pressure readings. With these readings a logical path of diagnosis can get your AC blowing cold as it should be. Read more on this subject if you plan on finding a mechanic to recharge the car air-conditioning.

I put together a repair modules section on my you fix cars website that talks about the theory and operation of car air conditioning. Understanding how the system works is very helpful for problem solving. You can also head back to this blog’s main page and get some more automotive repair information.

In this next video Pat Goss talks about things you can check at home before seeking service. This is good stuff and worth the 4 minutes. Note at the end Pat recommends professional service for charging AC systems. This might be a bit over cautious but he is right that it can be dangerous for inexperienced do it yourselfer’s. Mr Goss is for sure right that putting too much Freon in the system can destroy the compressor. It’s possible to do thousands of dollars in damage by doing it wrong! If you decide to go for it Read the instructions carefully.



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