Warm Air Conditioner, Need Advice

Zaphod

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2007 Mazda CX-9 AWD
Car is a 2007 CX-9 AWD

A month or so ago, my air conditioner stopped blowing cold air everywhere in the car (front and back). Doesn't seem to be any issue with the controls or the blowers, just getting warm air blowing out of vents. After some research, I'm a little nervous about just trying to recharge it. Anyone have any advice on this? A reliable way to check the pressure (maybe recommend a good gauge), and what's a good R-134a refridgerant that won't clog the system. Having trouble finding good information, but it seems there should be more to the process than just adding freon. But then again, the car does have over 130k, so maybe it does just need charged. Any help or advice is appreciated!
 
All R-134a refrigerants are identical. Some have added compressor oil or added leak stop. Compressor oil always circulates with the refrigerant through the system. Finding an oil drop is a good way to find the refrigerant leak.

All pressure gauges are OK unless they're defective (or so cheaply made that they can't work). In any case, one needs to know the expected pressure at the particular point in the system and adjust for the temperature of the day. The refrigerant pressure is temperature dependent, not quantity dependent unless the system is empty--then the pressure gauge will read zero or close to that.

So...if you're pretty sure the problem is loss of charge, not a defective part like a pressure switch or the compressor or its clutch, just add a can while the engine is running and the AC switched on. You should hear the clutch engage and the compressor start working as you add the charge. All you need is a can of R-134a and a charging hose. As the can empties it cools itself. You can put the chilled can into a container of hot tap water to warm it and get more out. More refrigerant is not better. The weight of refrigerant shown on the label under the hood is just right. If one can doesn't work, don't add another. "If a little is good, putting more on is better---The Moron Theory."

If the new charge works for only a short time, get the system fixed. I had a Volvo that needed one can a year. The refrigerant with the leak stop helped but didn't cure the problem, and I only used one can of that as long as I owned the car.
 
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