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    AC Not Cooling Car – Advice on Freon Leak

    2004 Hyudai Sante FeDennisB © Summary: Below is a series of questions and answers from a previous AC article of mine. A visual inspection is the first thing to do when looking for a refrigerant leak. Most car AC systems have UV dye which make looking for problems easier. If unsure about UV dye being in your car’s air conditioning system, look under one of the service port caps. A yellowish green may appear. It’s best to use a UV light, also known as a black light, when looking for the dye to reveal a leak, but sometimes it’s visible with the naked eye.

    Question from Mike – I have a 2004 Hyundai Santa Fe. The first time the problem started, it was blowing hot air. I noticed the clutch on compressor not kicking in. I added freon from local parts store and got cold air but noticed a bubbling around low line port schrader valve. The next day it blew hot again, changed schrader valve topped off freon to 45 on low side blew fine but by the next afternoon was hot again. Got home to find a lime yellow/green oily spot on floor in garage. What do you think?

    Answer – Mike, it’s common to have a few bubbles from the schrader when you first disconnect the hose. But, 45 is too high on low side, may of overcharged (at 1500 RPM’s). The dye on the floor could have been from the actual leak or from the system relieving itself of the excess pressure if it was overcharged. I would clean everything, make sure at least 50 psi is in the system with it off (static pressure) and check for leaks using electronic leak detector and/or UV light. Good Luck.

    From Mike : Thanks will try may get back to you soon.

    Mike’s follow-up – I checked around, under, and  atop engine compartment where a/c lines and compressor lies… Using a UV light (blacklight) found dye in the crease on the two piece housing of the compressor and nowhere else. Does this mean I may have overpressurized the unit and now need to replace it?

    Answer – Mile, you know there was a leak already, that’s why you added Freon. The dye on the seam of the AC compressor housing indicates a leak regardless of if you caused it or not. It should be replaced and the rest of the system should be checked (in case there’s more leaks). With an electronic leak detector, you can check all the AC components that are hidden like the evaporator (and expansion valve) in the dash. You most likely didn’t cause a leak because there’s a pressure relief valve that will vent pressure if needed. Sometimes the pressure relief valve is located on the back of the compressor and also most systems will turn the compressor off when the pressures reach around 450 to 500 psi on the high side. Good Luck.

    Mike – If no other leaks are found, can I replace just the compressor or do I need to replace the expansion valve or other components? Finances are tight. Thanks for your help.

    Answer – Mike, some compressor warranties will require the expansion valve and dryer to be replaced. Some will only require just the dryer to be replaced. If I had my choice and the compressor just leaked like yours and didn’t “lock up” which could put trash/debris in the system, I would replace the compressor and dryer and skip the expansion valve. Check with the parts store though to see what is required for the warranty. Good Luck.

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