Auto a/c cycles off even when set to max?

My a/c does not always blow cold air this summer so I got some r134a and a hose w/gauge from AutoZone (great price).





The air was set to max and on the highest setting. The gauge reading was normal (35-40), but then after a few minutes I saw it climb to 70 as the compressor cycled off. I thought when on max, the compressor did not cycle off???





Does this indicate a problem with the compressor or something other than just freon?

Auto a/c cycles off even when set to max?
hook your gauge back up to the low side. start AC on max with windows down on car. now bring your idle up to 1500RPM. watch your gauge the pressure will drop down below 35 then your compressor will cycle off. if this is what happens you are still slightly low on freon add a little more until the low side pressure maintains 35-45. my preference with r134a is 40.


if the pressure does not drop during this test and remains 35-40 you will need to have the high side pressure tested.





there are some other posibilities depending on year, make, model and which AC system you have.
Reply:All "MAX" does is recirculate the cabin air.


It does NOT control the pump.





The pump cycles depending on the pressure in the system.
Reply:the system is probably overcharged
Reply:you did not say what kind of car, or what the air vent temperature is in the car on high blower, max a/c max cold, the actual temp of the air leaving the dash is important, and each manufacturer has a spec for the "cycling" pressure which translates to a temperature.... if you got it to blow cold for a few dollars..... not great really. does it need oil? where did the old freon leak out of ?? see. its a can of worms with no easy answer... go the the shop in town that ONLY DOES A/C work, the second choice would be the dealer for that make and model and only if they have a mechanic with 10-15 years experience on that exact model.
Reply:It never ceases to amaze me that people think if they can buy something, they know how to use it. Buying these recharge kits from auto parts stores and thinking you can fix your A/C with them is kinda like having the money to go buy an airplane and then thinking you can fly it.
Reply:various things can cause the compressor to cycle off, high pressure, low evaporator temp and malfunctioning controls. if the system is cooling well now you probably don't have a problem. it should not cycle off at 35 - 40 though, but you did after all get a great price on the gauge. if you are still having problems take it to a pro. you can do some expensive damage if you don't know what your doing.

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