Auto Repair Q&A



Cooling System










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Air Conditioning Checklist

Auto AC system

As summertime approaches, it's important to make sure your car's air conditioning (A/C) system is up to snuff. It's better to check it now, before hot weather comes than it is later, when you need it and it doesn't work. This quick checklist will get you through the process of making sure your A/C system is ready for the summer.

Check Compressor

The first step is to check the compressor. With the engine off, check its bolts for proper tightness/torque. It's generally a good idea to do this with all engine accessories every year, so you may as well check the others while you're there. Check the accessory/serpentine belt(s) as well and replace as necessary.

The rest of our checks require that the car's engine be running. Safety precautions for working under the hood while the engine is running apply!

First, check for sounds that may indicate a problem. With the A/C system off, listen for knocking or grinding sounds that could be coming from the A/C compressor's vicinity. This may indicate problems with the mounting, the pulley or the A/C's own clutch.

Now turn on the A/C and turn up the blower (fan). Again, check for sounds under the hood such as squealing, grinding, or knocking. Look at the accessory belt as it turns the compressor: is it wobbling or bouncing? If so, it needs to be tightened and/or replaced.

Check for Cold Air

This might seem obvious, but now that you've got the air conditioning running, is there cold air blowing into the cabin? If it's set for cold (aka "Max A/C") and is only blowing lukewarm or slightly cool air, you have a problem. If it's blowing cold air as it should, you can proceed with the next check and you're probably A-OK.

In the case of cool or lukewarm air rather than cold, your issue is likely that you're system is low on coolant. This could be from a number of things, but most likely it indicates a leak. Our next check will look at that.

Check A/C Components

With the engine and A/C running, check all of your coolant lines (again, observing safety measures while the engine is running) for obvious leaks. Often these leaks will be at the fill points on the high pressure side. Look over the hoses to see if you can observe any leaks, cuts, weak spots, kinks, etc. You'll usually see an accumulation of dirt and grime around where a leak is occurring, even if the leak is too small to see with the naked eye.

Turn off the A/C and listen again for knocking or grinding, as above. Then shut off the engine and re-check those hoses, fittings, etc. on the A/C system. Use a gauge to measure line pressure on the low- and high-pressure sides, as indicated in your repair or owner's manual for your particular vehicle.

If you have leaks in your system, you'll need to consult with a certified technician as A/C systems are federally regulated and require specific tools and expertise to work with.

Clean the Condenser

Last but certainly not least, whatever your findings on the rest of the A/C system, now is the time to clean out your condenser and (while you're at it) the radiator on your car. With medium-pressure water or air, clean out the fins on the radiator and condenser. The pressure from a common garden hose is plenty. Your goal is to get the dirt and bugs out from between the fins as best you can in order to help airflow and improve their operation.