Ac system won’t equalize pressure.

[Stewartkyle44]

Hello, so I am at a loss. My tractors ac pressure (high/low) won’t equalize when charging. Low side goes up to 80-90psi while high side hovers around 50-80psi but won’t take any more freon. All proper steps have been taken per the service manual to evacuate and charge system. I have replaced compressor, dryer, and expansion valve. I have also blown out high and low side tube with compressed air to check for blockage. Not sure why system won’t equalize and take more freon to get the the right pressure which should be 206-213psi (high) 21-28psi (low). Any thought?

 

[K5lwq]

My first thought is compressor clutch is not engaging. Why was compressor replaced? Maybe give more information as to what was wrong and all the steps in order from the beginning.

 

[workinonit]

What freon is the system? It sounds like you aren't making up a low pressure cutoff switch but if you replaced the entire system then it could be anything. If you jump out the clutch will it come on so that you can get some additional freon in the system?

 

[Stewartkyle44]

@K5lwq compressor clutch is kicking on and off as it’s trying to pull in freon but won’t fully engage because the system isnt getting enough to trick the system to fully engage. It all started with the pressure relief valve on the back of the compressor blowing off sporadically. Slowly got worse and got tired of buying freon so I bought some of the main parts to tune it up since it’s a 2008 and probably needed it anyways.

 

[Stewartkyle44]

@workinonit the freon it calls for is R134a and that is what I am using. It seems the low pressure cutoff switch is working because the compressor clutch is disengaging because it’s at the threshold of to low of pressure to fully engage.

 

[workinonit]

The compressor needs to run long enough to get freon into the system. You were talking about the pressures equalizing, in order to get gas into the system you don't want the pressures equalized you need the low side to be much lower so the gas will enter the low side.

 

[Stewartkyle44]

@workinonit No matter how I introduce freon into the system the low side goes up to 80-90psi and the high side stops at 50-80psi. Shop manual says to introduce freon at the high side first with engine off the required amount 1.5lbs. Than close high side, start tractor, idle up to 2000rpms and than slowly introduce to the the low side until it reaches manufacturer recommended psi on high and low side during normal operating conditions.

 

[Harry in Ky]

@workinonit No matter how I introduce freon into the system the low side goes up to 80-90psi and the high side stops at 50-80psi. Shop manual says to introduce freon at the high side first with engine off the required amount 1.5lbs. Than close high side, start tractor, idle up to 2000rpms and than slowly introduce to the the low side until it reaches manufacturer recommended psi on high and low side during normal operating conditions.

Reading through your posts my first thought was you were charging the system with both valves on your gauge set open. This post confirms that you're not. My guess is you simply have a defective new component. Either the compressor is doing nothing or the expansion valve is open and not closing off flow. The valve being the most likely. The quality of replacement parts these days is dismal, and I'm not surprised by anything any more.

 

[Stewartkyle44]

@Harry in Ky That was my first thought. Bought the cheap ones first. Now I am on my second new compressor and expansion valve. Straight from manufacturer and still doing the same thing.

 

[LouNY]

What is your equalized pressure, system shut down and not ran for at least an hour and your ambient temp.

 

[Stewartkyle44]

@LouNY Yesterday it sat for more than an hour while I was researching stuff with engine off in about 80 degree temps outside the low side was 75psi and high side at 25psi. When the system settles that where it sits at.

 

[LittleBill21]

system should settle evenly, you sound like there is an obstruction somewhere in the system

 

[Stewartkyle44]

@LittleBill21 That is the only thing I can think of being the issue. Where could the obstruction be though? I pulled the low and high tube off the back of the compressor after evacuating and forced compressed air through the lines and could feel it coming out the other end.

 

[Stewartkyle44]

Maybe it’s something in the actual AC unit?

 

[LittleBill21]

could be in the cores or orifice valve, does your system have a dryer? was it replaced properly. blowing off the pressure valve definitely indicates some kind of high pressure that should not be there.

if you removed the suction side of the compressor, do you get a INSTANT release and equalization? if not you have issues up near the dryer evaporator or metering device.

 

[LittleBill21]

my uneducated opinion says its not the compressor, if the pressure is still uneven after sitting. i'd be looking at the orifice metering component, as its the smallest section in the system that could get clogged.

Feel like this would be a good place to use my thermal camera.

 

[Stewartkyle44]

@LittleBill21 The shop manual doesn’t say anything about the orifice valve. I don’t think it has one just the expansion valve which I replaced. It does have a dryer and I replaced that. I can’t remove just the suction side of compressor line as the low and high side lines use a special bracket that you have to mount or remove them at the same time.

 

[LittleBill21]

I'm only guessing at this point, since I can't see it, I understand about the bracket. maybe you can borrow a thermal camera, and see if you can see if there is a block somewhere in the cores.

 

[workinonit]

I've never seen one go to ambient with that much pressure difference. Even if you had a blockage it should equalize in the other direction. Almost sounds like a check valve is in backwards but I don't know what that would be unless the TXV is backwards. It's really strange that the suction pressure is higher than the discharge pressure.

 

[LittleBill21]

I've never seen one go to ambient with that much pressure difference. Even if you had a blockage it should equalize in the other direction. Almost sounds like a check valve is in backwards but I don't know what that would be unless the TXV is backwards. It's really strange that the suction pressure is higher than the discharge pressure.

i would agree he put it together wrong, other then the fact he was blowing pressure valves clean off before he started replacing things.