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On sweltering summer days, it’s nice to turn on the air conditioning. Otherwise, you’re stuck in a hot car until you can determine why your AC isn’t working properly. Several problems can arise with your AC. It could be an issue with the cooling fan, a clogged filter, or maybe even the condenser.

While problems with your air conditioning are tricky to diagnose, they don’t always require a trip to the auto shop to fix them. Don’t know where to start? Here are some tips to help you diagnose your vehicle’s AC problem.

Begin with the compressor

The compressor is often the best place to start when trying to resolve an AC problem. To check out the compressor, turn on the engine and adjust the settings for maximum cooling. Check to make sure the compressor’s clutch is engaged. You can do this by making sure the center component that engages and disengages the pulley is working.

If it’s moving fast, the refrigerant level could be too low. Low refrigerant can prevent the air conditioner from operating. The refrigerant could be low due to a bad component in the system or a possible leak.

If the compressor’s clutch isn’t engaging, use a voltmeter to check the amount of voltage making it to the compressor. If voltage gets through, the clutch might be faulty. If the clutch cycling switch is the culprit, the electromagnetic clutch won’t engage, the refrigerant won’t pressurize, and the system won’t operate.

The condenser

If your vehicle’s air conditioning is putting out mildly cool air, even with the settings cranked as high as possible, you’ll want to check your condenser. Make sure the condenser and radiator are both operational when the AC unit is on. If debris is clogging the condenser or it’s damaged, this could be the reason cold air isn’t passing over it.

You’ll also want to check the cabin air filter to make sure it’s not blocked or damaged. Next, examine all the system pressures using a manifold gauge set. Check the AC unit’s manual for recommended pressure settings to ensure everything is running properly.


Leaks are one of the most common culprits of air conditioning problems. Low pressure often, but not always, indicates a leak. One of the easiest ways to detect a leak in using a UV AC leak detection kit. The kit uses dye in the system, with a UV light to find leaks. If the system is too low and the compressor isn’t cycling as it should, this particular method may not work.

You’ll want to make sure all the fittings within the system are tight and secure. Check the hose manifolds on the compressor and inspect the hoses where they’re crimped onto the fittings.

Examine the front seal and the o-ring sealings on the pressure switches if you have them on the back of your compressor. Not all units have this. Check the Schrader Valves and look for pinholes in the condenser. Also, examine the area where condensation drains from the evaporator with a UV light. You may notice oil or dye, indicating a leak.

The next step

Once you’ve identified the problem, you may be able to make the repair yourself. If you can, you’ll get your vehicle’s air conditioning unit up and running quickly. If not, an experienced mechanic can repair the system. Pass along any information or discoveries you’ve made so they can help you get back into your vehicle’s cool cabin faster.