ac questin

anybody no what would cause ac compressor to kick out on low pressure side

depends on the system, could have a low pressure switch or a de ice switch or an evap core temp switch, probably others also. Is there more to this story?

Low on Freon is my thinkin. When mine get too low the clutch never pulls in at all,,,,then as I add Freon she starts short cycling,,,,,,then when Freon is replenished she holds in and cools.......

John T NOT an AC man NO WARRANTY

well started out high pressure maxing out found that prob to be stopedup condenser changed it run vaccum added right amount of Freon started unit low pressure side starts falling until compressor kicks system was full of die I must add

Did you replace drier and expansion valve, or the acumalator/desicant and the orifice tube? WAS the system full of 'stop leak'? What are your pressures? Sounds like low - lowside pressure-could be caused by stopped up expansion valve or orifice tube. Mark

(quoted from post at 18:17:02 07/09/13) well started out high pressure maxing out found that prob to be stopedup condenser changed it run vaccum added right amount of Freon started unit low pressure side starts falling until compressor kicks system was full of die I must add

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You haven't really clarified the system you are working on...the assumption is that you are talking about an automotive system. After having done all the above and have succeeded in changing the condensor coil and have added the correct quantity of refrigerant, I would suggest that the accumulator/drier also be changed.

If the condensor was plugged internally the accumulator/drier will also be severely restricted causing the drop in suction pressure which in turn drops the system off on the low pressure cut off.....PROVIDING that you have in fact added the correct amount of refrigerant.

...like John T....no warranty espressed nor implied. Good luck.

I'm sure there are more possible causes, but we ain't got a lot to work with yet....but it is always good money spent to change the drier with a major component replacement i.e compressor, condensor, severe leak on low side, evaporator replacement etc.......

yes has accumulator replaced low oressure falls to 10 where it kicks out never stabilizes high around 250 mabe 300 changed check valve I never had 1 do this im stumped

something else plugged, or low on freon.

its semi apu has low pressure switch I put new tube in also is it possible Freon machine faulty not adding enogh freon

I've had systems do similar in the past. There can be several different causes. One of the most uncommon ones I ran into was a line that had been made up WAY WAY too long that had been coiled up and zip tied in place. Thing is when it was zip tied it was also kinked to the point it was nearly collapsed.

Now on that same system when I first started on it my thinking was a stuck expansion valve. With that problem the compressor is pumping the refrigerant to the high side faster than the expansion valve can meter it through which results in higher than normal high side pressures and lower than normal low side pressures. Unfortunately changing it didn't solve the problem which caused me to begin looking further to find the kinked line. Bear in mind my customer had already spent nearly $3000 at the dealer to get the system operating, and the line I foudn kinked was a bran new line so I was about to pull my hair out before I found the problem with the line.

That all said, a restriction, of some type, between the high and low side is the only thing that's going to cause the problem your seeing. I say that because your high side pressure, in this case, is up in the range where it should be (at least in every 134A system I've worked on and read about). That being the case not having enough refrigerant in the system really isn't likely to cause the problem in an expansion valve system as the valve is going to meter refrigerant relative to the temp of the cooling evaporator core regardless of how much is in the system. In other words no refrigerant means the coil wouldn't get cold, which would cause the valve to shut, so it should be staying wide open. Because of that the pressure on the high side would typically be lower than normal just like the low side pressure.

Like another post suggested it could also be a problem with the reciever/drier stopped up, but you say you've changed that already so that shouldn't be an issue. Along that line of thinking could a plug, etc possbly have been left in/pushed into the port on one of the new parts vs being removed?

Beyond that I wish I knew what else to tell you to look for, but in the twelve years or so I've been working on mobile A/C systems the things I've talked about so far are all that I have been unlucky enough to run into. Good luck.

I am going to run one by you just for thought. I ran into this one time where a guy had changed out a lot of parts & some of them several times guessing what was wrong with it before they brought it to me & I found it had to much oil in it. I purged the system & refilled it with the correct amount of oil & it worked fine.

If low side pressure drops fast until compressor shuts off, then builds pressure, compressor comes on, pressure drops until it shuts off again, then that means you have something plugged in the system. it could be plugged anywhere in the system. I have seen deteriorated O-rings break apart and plug up ports, and I have seen people get water into the system, which creates ice and restricts flow. Does it get worse as it runs, or is it a steady problem? If it is steady, it is probably not ice.


You need to find the restriction.

There is no easy way to do that, except for attaching a shop air compressor hose to the low port with 35 psi, with a good drying system on the compressor. run the system, and start disassembling it from the low side of compressor back to expansion valve. When you remove the restriction, you will know it.


Warning, this is a pretty backwoods way to do it. definitely not recommended by ASE.

Probably shouldn't have even mentioned it... but it can be done.

(quoted from post at 18:44:55 07/09/13) its semi apu has low pressure switch I put new tube in also is it possible Freon machine faulty not adding enogh freon

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Some vehicles also have a high pressure switch in the power steering circuit wired in series with the a/c to cut off the a/c at low engine rpm while the wifey pegs the steering wheel to the left or right. There should also be a small screen in the liquid line directly before the expansion valve that could be contributing to the issue.

Does your system have an orifice tube?

Was the tube checked/changed during this "diagnostic" work?