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I am admittedly not much good with A/C. FIL has a 105U. Compressor will cycle on and off every 15-20 seconds. It’s halfway cold air, but compressor constantly cycles. Pressures when compressor is engaged- best I could tell no longer than it stays on- are 25’ish low side and ~400 high side. Expansion valve? Condenser is clean as can be. 

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Was freon recently added ? has any components been replaced ? What Machine is this A/C system on?

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how about the evaporator is it full, how about the oil cooler or radiator they full? if its not passing enough air thru the condensor in these temps regardless if its clean, it wont cool off and get too hot causing the high pressures, 400 is high im pretty sure so maybe because its so hot outside its cycling the high pressure side off/on? try running a hose on the condensor to cool it and see if pressures drop and it stays running while running the cool water across it, then you know its getting too hot and kicking out on the high side value. 

 

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Nothing has been done to system. Again, it’s a 105U. Tractor has around 1800 hours. FIL brought it down yesterday and said air didn’t work. He’s 82, and well, he didn’t have it cut on. I cut it on and could tell it was cooling but noticed rapid compressor cycling. 

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run cold water on condenser see if it quits cycling - ours works fine till it gets REALLY hot out adn then cycles sometimes and pressures go up on the 5088 so its borderline on pressures/charge - i was able to troubleshoot ours that way with the garden hose and it would stay running and not shut off/on, i didnt have a set of gauges so that was my tool of choice

 

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If you could find out the type of Freon it has it would help. Assuming it’s 134a then 400 psi is screaming high. 400 psi equates to 183 degrees f. On a 100 degree day your passing 100 degree air across the condenser. With 100 degree air you should be able to cool the Freon to 130 or 140 degrees. That would correspond to 200 to 230 psi on the high side. 400 psi on r134a should be the high limit safety. As Searcyfarms said run a water hose on it. Also just look at the condenser and see if it’s packed with debris.

good luck.

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9 hours ago, MarkG said:

If you could find out the type of Freon it has it would help. Assuming it’s 134a then 400 psi is screaming high. 400 psi equates to 183 degrees f. On a 100 degree day your passing 100 degree air across the condenser. With 100 degree air you should be able to cool the Freon to 130 or 140 degrees. That would correspond to 200 to 230 psi on the high side. 400 psi on r134a should be the high limit safety. As Searcyfarms said run a water hose on it. Also just look at the condenser and see if it’s packed with debris.

good luck.

That's what I was thinking that those pressures are really high. I just recharged a 7230 Magnum which is a lot bigger tractor than that. With help on here I learned what the pressures should be and it works like it should now.

We have a 105u as well. I don't know what yours is used for or what type environments it works in. Ours runs hay baler, grinds feed, has run corn planter in the past and pulls grain drill. Speaking from experience that radiator,condenser and oil cooler is notorious around here for getting packed full of dust and crap. There are pull out screens in front of everything that it seems like we're cleaning on a very regular basis. Even with those screens the radiator and coolers still get dirty and you have to blow them out every few months. We blew ours out during planting, starting 2nd cutting hay and probably will before filling silo since it's on the blower. 

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On 7/30/2021 at 8:15 AM, Reichow7120 said:

That's what I was thinking that those pressures are really high. I just recharged a 7230 Magnum which is a lot bigger tractor than that. With help on here I learned what the pressures should be and it works like it should now.

We have a 105u as well. I don't know what yours is used for or what type environments it works in. Ours runs hay baler, grinds feed, has run corn planter in the past and pulls grain drill. Speaking from experience that radiator,condenser and oil cooler is notorious around here for getting packed full of dust and crap. There are pull out screens in front of everything that it seems like we're cleaning on a very regular basis. Even with those screens the radiator and coolers still get dirty and you have to blow them out every few months. We blew ours out during planting, starting 2nd cutting hay and probably will before filling silo since it's on the blower. 

Basically it moves hay. Screens and condenser are clean as can be. I’m thinking it’s something internal. 

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24 minutes ago, highcotton said:

Basically it moves hay. Screens and condenser are clean as can be. I’m thinking it’s something internal. 

ok so lets think about this some more, im no expert or claim to be, dont work on AC stuff because of no tools BUT I do have a logical brain that helps break things down

here is what my limited knowledge understands about ac systems

1) Air has to move thru radiator/oil cooler/condenser to cool refrigerant - low cooling/air movement can cause high pressures

2) too much refrigerant can cause high pressures - if nothing has been added or changed on system doubtful this is the case unless it was marginal and the HIGH outside temps are causing the issue thus the reason for cooling condenser with water to see if it would cycle properly and bring pressures down

3) a stuck high pressure cut off regulator/switch/valve if you will, can cause this BUT since you state its cycling off/on and pressures are high, this appears to be working

4) a clogged up evaporator could cause elevated pressures - do you feel good airflow from your vents or does it seem like its not very good anymore and you have to run fan speed on HIGH to get good airflow where you used to get plenty on lower fan speeds? 

5) a stuck expansion valve can cause excessive pressures - i do not know if your system uses and expansion valve or an orifice tube to regulate the freon but if you are having a failing compressor and metal is starting to infiltrate the system, it could clog the orifice tube or stick the expansion valve and make things go high pressure.

so my offering with my limited knowledge woudl be this........

1A) airflow restriction somewhere - fan belt slipping, radiator/oil cooler restricting airflow across condenser, evaporator clogged

2A) failing compressor that has distributed debris in the system causing orifice tube to clog up, or expansion valve to stick

3A) defective expansion valve ( if so equipped ) 

not sure if that helps but its something to ponder - 

 

 

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Don't know anything about 105u. If this is expansion valve system. What people seem to be missing is low side pressure. With condenser problem I would expect 40-60 psi low side. High highside pressure can be to much freon in to small a space. Can be confirmed by comparing reciever temp to gauge temp. I would want a glance at expansion valve while operating. My guess is it is frosting and op's first guess is correct. Just armchair ruminations and subject to failure.

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23 hours ago, highcotton said:

Basically it moves hay. Screens and condenser are clean as can be. I’m thinking it’s something internal. 

what didja find? 

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FIL got tractor to shop yesterday. I did little actual looking in the field when I noticed cycling/pressure issue- they were moving hay when I went to check it. Let’s’s just say BIL’s idea of clean as can be and mine aren’t the same- slid condenser out it was pretty stopped up. Screen in front was clean, condenser not so much. In process of blowing out CAC, condenser and radiator. One day I’m gonna learn to check everything myself, stay tuned....

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Cleaned condenser, CAC, and radiator after church. Low side now 25 and high side around 285. No cycling and cold air. Lesson on taking others word for things learned, but considering the alternatives it could have been worse. 

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1 hour ago, highcotton said:

Cleaned condenser, CAC, and radiator after church. Low side now 25 and high side around 285. No cycling and cold air. Lesson on taking others word for things learned, but considering the alternatives it could have been worse. 

285 is still pretty dang high on the high side

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3 hours ago, highcotton said:

Cleaned condenser, CAC, and radiator after church. Low side now 25 and high side around 285. No cycling and cold air. Lesson on taking others word for things learned, but considering the alternatives it could have been worse. 

oh man funny you say that, i have one of those same friends that has the same eyes when it comes to how clean teh radiator is, or how clean the oil cooler is and the AC condenser. funny how stuff varies in perspectives. 

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On 7/31/2021 at 8:53 AM, searcyfarms said:

 

4) a clogged up evaporator could cause elevated pressures   
 

 

5) a stuck expansion valve can cause excessive pressures - i do not know if your system uses and expansion valve or an orifice tube to regulate the freon but if you are having a failing compressor and metal is starting to infiltrate the system, it could clog the orifice tube or stick the expansion valve and make things go high pressure.

 

 

Ok ,  not trying to be a smart ass here but I have a comment  about the  #4 and #5 , if I may.

 

If the airflow across the evaporator becomes compromised for what ever reason ( iced up, dirty filter, fan motor quit, fan blade came off and what ever else you can think of ) it won’t cause any of your pressures to be elevated . It will  actually do just the opposite .   Your eveporator pressure will decrease and with the lack of any load on the compressor your condensing temp/ pressure will also decrease as long as everything else is still working.  In a nut shell a lack of air flow across the evaporator will never cause excessive condensing temp/ pressure. 
 

now regarding your #5 

 

At your metering device wether it be a cap tube, an expansion valve, or an orifice , when you become restricted at that location your refrigerant flow has now either stopped or nearly stopped . Now your compressor has nothing to compress.  In this scenario your evaporator pressure will reduce to nearly nothing and if your completely shut off at your metering device you will even see your suction pressure go into a vacuum .  ( that’s those red numbers on your Gauges below zero .) 

 

Dosent make sense??    Ok try this at home.   Start up your air compressor , let it start to fill and then slap your hand over the air intake.  It wil keep running but what ever the air pressure in the tank is at that time will be all you get.   It works the same in a refrigeration system . Stop the refrigerant flow and everything comes to a stand still.   Stopping the refrigerant flow at the metering device will not raise your condensing pressure but there is one thing not mentioned yet that will. 
 

He said the tractor has never been messed with so this is NOT relivent to his scenario but FYI , one easy way to get excessive condensing temp/ pressure is with the introduction of air in your system . Air is a non condensable and therefore even the smallest amount of it will result in high condensing temperatures. 
 

How can air get in you might ask???

The most common way is when people keep adding Freon and adding Freon and adding Freon without fixing the leak. These machines don’t consume the refrigerant if there is never a leak or your system has never been opened up for service then it will never need Freon and I mean NEVER!!!!!  
 

When a system looses enough refrigerant to allow the compressor to run below atmospheric ( or zero on your gauges) Then air is introduced through the leak because the compressor is running in a vacuum . 
 

OK now everyone’s gonna say well it should never run in a vacuum because the low pressure switch should prevent that .
And they’re right as long as that switch works . Another way Air can be introduced into the system is through your gauges if they are not purged properly. There can also be air in your system if you have had it apart for service and did not use a vacuum pump before recharging. These are all common things that any service tech should know before working on your system.

Regardless keep in mind that a noncondensible in the system will cause the pressures  he described. 
 

Also know that a Vacuum pump serves another purpose. Not only does it removed noncondensible‘s from your system but any moisture inside has now been allowed to boil off and be removed by evaporation. 
 

A properly evacuated , leak free system will be void of all moisture and air , both of which are considered to be a non condensable .

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3 minutes ago, lorenzo said:

Ok ,  not trying to be a smart ass here but I have a comment  about the  #4 and #5 , if I may.

 

If the airflow across the evaporator becomes compromised for what ever reason ( iced up, dirty filter, fan motor quit, fan blade came off and what ever else you can think of ) it won’t cause any of your pressures to be elevated . It will  actually do just the opposite .   Your eveporator pressure will decrease and with the lack of any load on the compressor your condensing temp/ pressure will also decrease as long as everything else is still working.  In a nut shell a lack of air flow across the evaporator will never cause excessive condensing temp/ pressure. 
 

now regarding your #5 

 

At your metering device wether it be a cap tube, an expansion valve, or an orifice , when you become restricted at that location your refrigerant flow has now either stopped or nearly stopped . Now your compressor has nothing to compress.  In this scenario your evaporator pressure will reduce to nearly nothing and if your completely shut off at your metering device you will even see your suction pressure go into a vacuum .  ( that’s those red numbers on your Gauges below zero .) 

 

Dosent make sense??    Ok try this at home.   Start up your air compressor , let it start to fill and then slap your hand over the air intake.  It wil keep running but what ever the air pressure in the tank is at that time will be all you get.   It works the same in a refrigeration system . Stop the refrigerant flow and everything comes to a stand still.   Stopping the refrigerant flow at the metering device will not raise your condensing pressure but there is one thing not mentioned yet that will. 
 

He said the tractor has never been messed with so this is NOT relivent to his scenario but FYI , one easy way to get excessive condensing temp/ pressure is with the introduction of air in your system . Air is a non condensable and therefore even the smallest amount of it will result in high condensing temperatures. 
 

How can air get in you might ask???

The most common way is when people keep adding Freon and adding Freon and adding Freon without fixing the leak. These machines don’t consume the refrigerant if there is never a leak or your system has never been opened up for service then it will never need Freon and I mean NEVER!!!!!  
 

When a system looses enough refrigerant to allow the compressor to run below atmospheric ( or zero on your gauges) Then air is introduced through the leak because the compressor is running in a vacuum . 
 

OK now everyone’s gonna say well it should never run in a vacuum because the low pressure switch should prevent that .
And they’re right as long as that switch works . Another way Air can be introduced into the system is through your gauges if they are not purged properly. There can also be air in your system if you have had it apart for service and did not use a vacuum pump before recharging. These are all common things that any service tech should know before working on your system.

Regardless keep in mind that a noncondensible in the system will cause the pressures  he described. 
 

Also know that a Vacuum pump serves another purpose. Not only does it removed noncondensible‘s from your system but any moisture inside has now been allowed to boil off and be removed by evaporation. 
 

A properly evacuated , leak free system will be void of all moisture and air , both of which are considered to be a non condensable .

thanks for teh clarification and info, wish i knew more.........hopefully i can remember all this when I am working on stuff - prob why i dont do AC work just ponder all the going ons of it

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I'm gonna throw one more thing as I didn't see it mentioned in this thread. Never been around a 105u however the newer tractors especially new holland influenced like to run an A/C cycle switch. Electrically it measures the temp at the evaporator coil up top and will cycle the power to your compressor. My 7840 had one go bad and the neighbors jx95 did as well. It's a little black box with like 4 wires, and a temp sender attached right next to the expansion valve up top. They apparently want that compressor to cycle some for whatever reason. My Ford will ice you out of the cab but the compressor still cycles on a 95* day. You dont really feel it in the cab but I can hear it cycle so I know it is. Maybe some of the A/C guys can chime in on the theory here. 

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so i have seen this before one in a blue dress,compressor cycling,head press 325,hooked guages, thermometer in dash and bled pressure down till temp stayed constant and press.down.the second one in a red dress turned out to be viscous fan clutch would not lock,just saying

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22 hours ago, snoshoe said:

Evaporater temp switch. To keep evaporator from freezing over. Most systems do that.

Thanks snoshoe. I knew what it did, but I was lead to believe the newer systems were more designed to cycle more often instead of the older systems especially designed for R12 that had trouble cooling on 134a and never would cycle under a hot day. Yes no? I guess I brought that up because my newer ford will cycle on a 90* day leading some to believe theres an issue when the duct temp never drops below normal.  I know this is just my thought process anyway. 

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OK. I can think of four reasons for disengaging the clutch.

1. Pressure to high

2. Pressure to low

3. Evaporater to cold

4. Cabin has reached set temp

On older systems 3 and 4 were actualy the same control. The temp control only measured and adjusted evaporater temperature. Newer electronic controls actually measure cabin air temp. Does that help?

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13 hours ago, snoshoe said:

OK. I can think of four reasons for disengaging the clutch.

1. Pressure to high

2. Pressure to low

3. Evaporater to cold

4. Cabin has reached set temp

On older systems 3 and 4 were actualy the same control. The temp control only measured and adjusted evaporater temperature. Newer electronic controls actually measure cabin air temp. Does that help?

Yes sir. Pretty much sums it up. Thanks again as usual. 

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