You expect your car’s air conditioning system to deliver cool air on those too hot to handle days. At some point, however, a problem may emerge, one that could challenge your abilities. Air conditioning repair is not always a simple do-it-yourself project. While air conditioning systems in automobiles have been around for decades, the operation of the system itself is based on a precise balance of physics. Here’s how to know when to DIY or trust the job to the experts.
Rule Out the Easy Problems
What’s keeping cold air from flowing from your air conditioning system? Before you worry that either the compressor, evaporator or the condenser is the problem, consider the easy issue first. Set your air conditioner to “fresh air” and place it on its highest setting.
First, if air isn’t flowing, a fuse may have blown. Locate the fuse box, with the help of your owner’s manual, determine which fuse supplies electricity to the air conditioning, and replace it if the fuse has blown. On most vehicles there is a fuse for the blower motor itself. If the fuse is good but the blower motor does not spin, try changing the fan speed from low to high one at a time. If the fan comes to life on one setting but not on another, you may have a bad fan speed switch.
Second, if the fuse is OK and air is blowing, but you sense an obstruction or detect an odd smell, then locate the cabin air filter. Cabin air filters are routinely placed in the glove box, beneath the dashboard or under the hood and adjacent to the firewall. Your owner’s manual can help you locate your cabin air filter. A clogged or dirty air filter can impede air flow and contribute a foul odor but is an easy replacement. If the cabin air filter is fine then you make have a blocked fresh air intake. lift the hood and inspect the area around the windshield cowling. Any build up of leaves, sticks and road debris near the air intakes can impede air flow, contribute foul odors, or both. Try removing the blockages and retesting the system.
Third, if air is flowing, but you’re hearing an odd sound coming from the vents, then your compressor may need replacing. You may hear ticking, clicking, squealing, or even banging when the air conditioner compressor is engaged. You can verify that the noise is coming from the air conditioning compressor by comparing the sound when the AC system is activated versus when it is off. If the noise only happens when the air conditioner is on, then a big repair may be necessary.
Fourth, examine the AC condenser. Look at the front of the AC condenser, typically located immediately behind the radiator. A build up of leaves and dirt can impede air flow, therefore, clean the area and try the AC system again. If the fins on the condenser look bent over or missing, you may have picked up a piece of road debris which caused damage. Anything puncturing the tubes within the condenser would cause a leak of the refrigerant.
Consider the Intermediate Problems
You’ve ruled out the easiest problems, now it’s time to get under the hood to discover what’s really going on.
Low refrigerant can cause AC problems. Leaks are difficult to detect as the R-134a refrigerant used produces gas, not liquid. Special refrigerant detecting dyes and devices can find leaks. An oil & dye injector kit will get the job done, just make sure it is compatible with your refrigerant type (R12, R134a, or 1234yf). There should be a sticker underneath the hood that specifies which type of refrigerant your system uses.
If the refrigerant is low, invest in an AC recharge kit. Each kit comes with refrigerant, gauge and instructions to help you put in the right amount of refrigerant. Again, make sure it is compatible with your refrigerant type. Follow the directions included with the kit precisely. If the AC starts working again, you will still need to find the leak or else you will just have to add refrigerant again eventually.
Onto the Hard Stuff
If your air conditioner still doesn’t work after investigating these possible issues, then you may be looking at a far more difficult repair project. Even so, there are a few other things to check before you delve deeper.
Start with the car’s radiator fan. If it isn’t working, a fuse may have blown, a wire may be frayed or a sensor might be bad. If it is an engine driven mechanical fan then the clutch may have gone bad. Either way if air isn’t moving through the AC condenser, you won’t have cool air conditioning.
Inspect the compressor clutch to ensure it is engaging. Look at the center of the compressor pulley. If should spin when engaged and stop when disengaged. When the center of the pulley is spinning, the refrigerant is being compressed as it should be. If it isn’t, check the fuse which can be found in your owner’s manual. If the fuse is OK, remove the compressor clutch relay and check for power and ground on the relay control coil terminals in the socket.
It’s at this point that air conditioner repair can test your skills or even be beyond you, especially anything involving the compressor, condenser, accumulator, evaporator and the orifice tube or expansion valve. Some say to leave this job to the experts. The cost of the tools required and understanding precise measurements alone may have you turning to a mechanic. Also the environmental laws surrounding air conditioner repair mandate reclaiming refrigerant whenever work is being done to the system, which requires an expensive reclamation machine. For these reasons it can make sense to let the experts are your local NAPA AutoCare take care of the problem.
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Photo courtesy of Matthew C. Keegan.
Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.