M7060 AC question

[psdstu]

I have been having an issue with my AC clutch cycling.

Whenever the Low side pressure starts to drop below 28psi the clutch cycles off, pressure then increases to 30 psi and the clutch engages again. As I understand the low side pressure should run between 22-28 psi. My clutch wont let it drop to less then 28.

The charge level is fine, no bubbles in sight glass and high side is between 190-240 with air temps above 85, and engine rpm at 1500.

I have cleaned the condenser as well as the evap coil and they are fine.

Just don't understand how the low side is supposed to be 22-28 psi, but the pressure switch kicks out the clutch at 28 psi?

Any suggestions would be appreciated.

 

[DaveFromMi]

If those pressures are accurate, it sounds like the pressure switch setpoints have drifted. What is the blower speed setting? High blower speeds would cause the cycling frequency to be less.

 

[psdstu]

If those pressures are accurate, it sounds like the pressure switch setpoints have drifted. What is the blower speed setting? High blower speeds would cause the cycling frequency to be less.

You are correct..... if I keep the blower speed at 4 the low pressure raises to around 31-32.... the more I lowers the blower speed the faster the clutch cycles.... not sure what to make of that.
Evaporator on the outside is clean..... wonder if the inside might be contaminated/plugged?

 

[DustyRusty]

You say that it is clean, however, it might not be. How did you clean the condenser and evaporator coils?

 

[psdstu]

You say that it is clean, however, it might not be. How did you clean the condenser and evaporator coils?

I used coil cleaner on the evaporator coil, condenser, and also cleaned the radiator real well with water.

 

[DustyRusty]

Thumbs up for doing it correctly. So many people blow them out and call it clean.

 

[mcmxi]

Just don't understand how the low side is supposed to be 22-28 psi, but the pressure switch kicks out the clutch at 28 psi?

According to the WSM, the low pressure sensor factory spec is 28 psi and the high pressure sensor factory spec is 455 psi. In the servicing section those values are 22-28 psi and 190-240 psi respectively.

 

[psdstu]

According to the WSM, the low pressure sensor factory spec is 28 psi and the high pressure sensor factory spec is 455 psi.

I agree.... which makes it confusing when the WSM says low side pressure is supposed to be 22-28... how is that going to happen?

 

[mcmxi]

I agree.... which makes it confusing when the WSM says low side pressure is supposed to be 22-28... how is that going to happen?

Is your A/C cooling effectively despite the clutch cycling on/off a lot?

I read the manual as saying that 28 psi is the ideal, but if the low pressure side is between 22 and 28 psi then that's acceptable. Kubota probably buys the low pressure sensor and there's a spec (range) on how accurate they are and that's reflected in the range given.

 

[mcmxi]

I assume you've looked through the A/C trouble-shooting section of the WSM. There's nothing specifically about the compressor clutch engaging/disengaging at an abnormal rate, but my experience with cars and trucks over the years has been low or contaminated refrigerant, or some kind of internal restriction in the condenser, dryer, evaporator etc.

I agree with your thought process of cleaning the condenser and possibly the evaporator too.

 

[psdstu]

Is your A/C cooling effectively despite the clutch cycling on/off a lot?

I read the manual as saying that 28 psi is the ideal, but if the low pressure side is between 22 and 28 psi then that's acceptable. Kubota probably buys the low pressure sensor and there's a spec (range) on how accurate they are and that's reflected in the range given.

Definitely.... I'm getting 40deg air out of the vents here in Florida.... so it's cold... just not happy about the clutch cycling. Guess it is what it is.

 

[motorhead]

Have you checked your inside air vent temperature? If you are at 38-45 degrees on recirculation mode, you are fine. Recirculation mode will cool better and also keep your evaporator cleaner because you are not letting the dust laden air inside through your evaporator. Also, when on recirculation, the ambient air is already cooler and the A/C will cycle. You also have a relatively small area of the cab to cool. I have a 2007 Dodge trick and the A/C compressor regularly cycles under normal running conditions.

 

[mcmxi]

Definitely.... I'm getting 40deg air out of the vents here in Florida.... so it's cold... just not happy about the clutch cycling. Guess it is what it is.

Oh ... well that's good. Is it hot and humid down there at the moment? Did you clean the air filter for the A/C system? There are the recirculate and outside air filters for the A/C system. Any chance that your evaporator is icing up when you lower the blower motor speed? I would thoroughly check that you're getting sufficient airflow through the cabin filters and evaporator. Also, check the A/C compressor belt.

 

[Fedup]

I agree.... which makes it confusing when the WSM says low side pressure is supposed to be 22-28... how is that going to happen?

I think you're looking at this from the wrong direction. The pressure switch on this (or any A/C system) is on the high pressure line usually up in the cab area near the evaporator. It's not monitoring the low pressure side of things at all. More likely your cycling condition (right or wrong) is related to the thermostat, not the pressure switch.

 

[DaveFromMi]

<22 psi - compressor shuts off due to low pressure (freeze protection)
>28 psi - compressor kicks back on
> 455 psi - compressor shuts off due to high discharge pressure (compressor protection & prevents blowing the charge)
What is the cycling rate? ~3 cycles per minute when in fresh air intake, high blower speed and ambient not hot is normal.

 

[jaxs]

Definitely.... I'm getting 40deg air out of the vents here in Florida.... so it's cold... just not happy about the clutch cycling. Guess it is what it is.

Not necessarily, short cycling is hard on compressor and inevitably shortens life of compressor. I realize that people think silver bullets can be found at online forums but that is far from true. Due to fluctuating compressor rpm and other issues, motor vehicle air-conditioning is 10x more challenging than 240 volt systems. Add the fact that home ac technicians have to meet a few requirments and most specialize whereas vehicle ac work is done by folks that also do brakes, carburators, ignition and a dozen other things you are looking at the perfect storm. I recommend you find the best technician you can and cut your lose down the road. There are no less than a dozen reasons why your ac might short cycle and only one who understands how system works can solve it WITH HANDS ON. Wag,wag wag wag wag

 

[mcmxi]

Not necessarily, short cycling is hard on compressor and inevitably shortens life of compressor. I realize that people think silver bullets can be found at online forums but that is far from true. Due to fluctuating compressor rpm and other issues, motor vehicle air-conditioning is 10x more challenging than 240 volt systems. Add the fact that home ac technicians have to meet a few requirments and most specialize whereas vehicle ac work is done by folks that also do brakes, carburators, ignition and a dozen other things you are looking at the perfect storm. I recommend you find the best technician you can and cut your lose down the road. There are no less than a dozen reasons why your ac might short cycle and only one who understands how system works can solve it WITH HANDS ON. Wag,wag wag wag wag

Most if not all of what you say is true, but it's always a smart move to do or check the basics such as making sure that the evaporator and condenser coils are clean, that the air filters for inside/outside air are clean, that the A/C compressor belt is properly tensioned. If the problem persists then it's time to consult the dealer or an A/C repair shop.

I have a Jeep TJ that I've owned for close to 25 years. A coupe of years ago I started to see A/C cooling issues and ended up spending around $800 at a local automotive repair facility who replaced a number of components. It's been good ever since.

 

[jaxs]

Most if not all of what you say is true, but it's always a smart move to do or check the basics such as making sure that the evaporator and condenser coils are clean, that the air filters for inside/outside air are clean, that the A/C compressor belt is properly tensioned. If the problem persists then it's time to consult the dealer or an A/C repair shop.

I have a Jeep TJ that I've owned for close to 25 years. A coupe of years ago I started to see A/C cooling issues and ended up spending around $800 at a local automotive repair facility who replaced a number of components. It's been good ever since.

My response was regarding op saying "Guess it is what it is". The message is that allowing short cycle to continue will likely lead to more harm and cost more to fix than biting bullet and having it fixed now. I'm all about diy "IF YOU KNOW WHAT YOU ARE DOING" but op has hooked gauges to his system and his questions don't sound like the voice of experience. I don't intend to shame nor belittle,to the contrary I'm just pointing out that with ac improper procedures are akin to exploratory surgery using unsanitary instruments. A neighbor once called to ask how to remove oil pan from his car and I told him every nut and bolt inside require far more expertise than removing pan so leave it be. Had he asked to borrow plasti-guage or torque wrench I wouldn't give it second thought before accommodating.