I have a 2009 L4330 with 750 hr. When engine rpm is below 1800 the air does not cool. I have cleaned condinser and evaprator, put in a heater line shut off, the belt is tight and there is no evidence of the cluch sliping. When engine is above 2200 rpm low side is around 45psi and high side is around 120 to130 psi it cools to about 12 to 14 degrees below ambiant, but below 1800 rpm there is no cooling. I don`t believe the system has ever ben opened so air and mosture are unlikley. I have had the tractor for 7 years, before that it had only had dealer service. Does anyone have an idea what could be wrong or a way to improve Airconditioning??
Weak air conditioning
- Thread starter lawnmower
- Start date
Meaningful pressure readings require knowing the ambient temperature. Your high side pressure reading could be OK or 100# too low. I'm guessing it's low. Here's a pic of a thermometer stuck into a vent on my L4240 on a hot day.
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Old Machinist
Well-known member
Equipment
Kubota LX3310 cab, JD 4310, NH 575E cab backhoe, JD F725, Swisher 60", etc.
I would evacuate, vacuum, and recharge with the correct amount of refrigerant to start.
In my experience your pressures are way off. I've rarely seen a system (R134A) run properly at over 25 PSI on the low side. I usually get get good results between 15 and 20 on a hot day. Your high side seems way low to me. I'd expect 150 to maybe near 300 on a hot day, particularly so on Kubota systems with a small condenser and usually so far in front of the radiator. At lower RPM there is little or air flow through it so pressures usually get pretty high. If you see 130 PSI and it's working at all that sounds strange to me.
As for being low on charge. Possible, yes. What is the static charge with system off and pressures equalized? On an 80 degree day I would expect to see 70 to 75 PSI on both sides.
As for being low on charge. Possible, yes. What is the static charge with system off and pressures equalized? On an 80 degree day I would expect to see 70 to 75 PSI on both sides.
I went to the garage and checked, the temp is 75 today and engine off psi was 80psi on high side and a little over 75 on low side. I started the engine with the air on high and the high side went to about 95psi and the low went to about 65 psi with the engine at 1000 rpm. I am not fimilar with 134A systems, I worked on auto air conditioning back in the R-12 days. I defenatly don`t have even close to the pressures you listed. Were to look first is the big question?
Ok, recharge first. If that doesn't change things, could be a faulty TXV or compressor.
I will recharge, but if i`m going to empty the system vacccum it and charge it I can change the expansion valve and dryer for about $70 or $80 bucks more with after market parts. This would give me more info as to the condition of the compressor. I think that is the direction I will take. Has anyone had good experiance with after market air parts? I see ads for a hole new after market air system for my tractor for under a $1000 bucks. Has any one tried the after market parts?
Your static pressure is about right, certainly not low. The pressure differential in the system is the primary job of the expansion valve. The pressures you're seeing now tell me your valve isn't closing down quite enough while in operation. Low side pressure is too high, the high side pressure is too low. I'm surprised you get much cold air at all. If this were my project I would be replacing the valve and the drier and see what effect that has. I would get Kubota parts, not after market. Your choice.
Old Machinist
Well-known member
Equipment
Kubota LX3310 cab, JD 4310, NH 575E cab backhoe, JD F725, Swisher 60", etc.
Ideally not more than 30 psi on the low side or 250 PSI on the high. Results can vary depending on humidity and other conditions.
When the compressor clutch turns off the pressures will begin to equalize.
Old Machinist
Well-known member
Equipment
Kubota LX3310 cab, JD 4310, NH 575E cab backhoe, JD F725, Swisher 60", etc.
Not used any parts on my Kubota AC but I have used aftermarket parts on my cars and backhoe without any problems.
Curious about the 15 to 20 low side pressure. Most of the Kubota Tractors run between 20 - 28 on the Low side with the Low Pressure switch set at 28 psi.
How does the system operate at that low range when the LP switch kicks off the compressor at 28 psi, never allowing the system to drop to 20-28 psi?
If that tractor was under my supervision & it had a very clean exterior of radiator, condenser, evaporator & cab filters I'd add more refrigerant to get pressure up to match chart shown below for your current ambient temperature. With 80°F ambient temp your tractors AC system high pressure should be 175-210 psi not 130 psi.
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The low pressure switch is on the high side. That side should never be below 30 or so PSI. If static pressure is at 30 or less the system should not be operating.
Try adding a 12 oz can of R134A to the system (without the "sealer" ) and see if it makes a difference. If it does, then you can decide if you want to add more or just evacuate and refill. To do the job correctly, you need to know how much is in the system, just like you did with the R12 and only fill to the specification. Sometimes you don't have the luxury of doing it this way, so adding some slowly might be the best that you can do. On the R12 systems, you had the sight glass to assist in getting the charge close.