This is a beginners tutorial on how your automotive (134a) air conditioning system works. Hopefully this gives beginners and diy owners an idea of how their system works and how to diagnose certain problems.

AC gauge set and pump kit:

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  1. Steven Bull

    Which valves are open when you hooked up that pressure test?

  2. Junior Miller

    I got a 2008 Dodge Caliber a/c worked great for a few months not it just blows hot air. It holds a vacuum what could it be ??? Btw it’s the wife’s and we have a week old baby need this fixed ASAP

  3. Jett Rink

    Thank you for your speaking loudly and clearly… so many people these days just mumble. good video

  4. Mitchell Bonomi

    I have replaced the condenser, evaporator, expansion valve and the compressor and have no leaks and pressures are fine and the fan works fine, but still the air warms up at a stop or idle…Any clues on what the problem could be?

  5. zazen69

    Do you have to add oil to the condenser and drier valve? I thought you just have to add PAG oil to the compressor. I'm planning on replacing a compressor with a seized clutch along with the condenser and drier valve and then having it professionally evacuated and recharged. Should I tell them to add more oil and UV dye?

  6. Anas Alamri

    Thank you Sir. Very informative to the regular person.

  7. Beach&BoardFan

    Where'd you get that relay switch from?

  8. Luis A Meneses

    So I did the dynamic check and my lo pressure fluctuates rapidly between 41 and 43 psi, the HI pressure is sitting around 170 psi. Is it normal for the lo to fluctuate like that?

  9. tecnico

    Just an observation it is vacuum 'pump'…no vacuum compressor.

  10. Fusang Tartarian

    Does the Expansion Valve open and close when Window defroster is on? The reason i asked is that i turned heater on with defroster and then switched to cold air and my AC began to work properly,,,,,,,,…….for a day then went back to fluctuating cold and warm air.. So did i give the expansion valve a kick in the butt…. i live in lower desert , Oasis, Ca.

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