M9000 A/C system

[dvcochran]

Hello,
Thanks to anyone who can help. I recently purchased a 2003 M9000 cab tractor with 789 certifiable hours. The tractor sat outside confiscated by the DEA for 7 1/2 years. It runs out very well but I bought the tractor before I found out about the apparent chronic A/C issues. When purchased, the compressor would run but the air was not very cool so I thought it may just need a charge. Per my local Kubota dealer (who deals mainly in B and L series units) I changed the expansion valve and dryer. I have access to a recovery system so I changed the parts, pulled a vacuum for two hours, and recharged the system with the recommended 2.5xxx pounds or 134. The tractor cools very well now but the high side pressure climbs until reaching 450 psi where the compressor drops out. Spraying the smallest amount or compressed air across the condenser keep the high side pressure between 300 - 350 which seems high to me. Note: I removed the radiator and condenser and made certain the fins (cooling area) is clean and unobstructed. The low side pressure seems good at 35-40 psi.
The condenser is about 3" from the radiator so I tried sealing the gap with pipe insulation but is made no difference. Does anyone know of a "recall"/upgrade to fix this problem? It is terrible that Kubota would produce a cab tractor with such a weak A/C system. While on the topic, does anyone know of a high velocity cabin fan to replace the slow turning factory unit?
Thanks for any help,
David Cochran

 

[torch]

What is the low side pressure doing when the high side skyrockets? One would expect a low side pressure of around 25-40 psi.

I cannot speak to that particular model, but here's some general AC troubleshooting tips:

If the LP is low while the HP is extremely high then the two most likely causes are a restriction in the high side of the system or an excessive oil charge.

If the LP is high while the HP is extremely high, then there's a number of possibilities:

1. Air (or other contaminants) in the system
-- not likely air, you pulled a good vacuum. But did you purge the charge hose(s) before filling?

2. Overcharge of refrigerant
-- not likely since you filled by weight.

3. Excess oil in system

4. Condenser fins clogged or obstructed or debris trapped between condenser and radiator
-- sounds like you already checked for this.

5. Defective cooling fan(s)
-- is the fan thermostatic or electric? It is interesting that flowing compressed air helps the situation. (most guys do this test with a fine water mist, but whatever works... )

6. Overheating engine

7. Incorrect refrigerant
-- I assume "with the recommended 2.5xxx pounds or 134" means you filled with R-134a? Did you get it from a reputable source? Believe it or not, but there is a serious problem of counterfeit R-134a coming primarily out of China, with R-40 (methyl chloride) being substituted for some or all of the contents.

That's all that comes to mind at the moment...

 

[Tx Jim]

Welcome to OTT
I'll add to what torch stated loose or worn compressor belt or possible faulty compressor.
Adding an electric fan in front of condenser might also help.

I owned a M4900 that everything had to be spiffy clean for the AC to cool very good down here in the Texas summers.

 

[Bulldog]

Have you checked the cab air filter? It should also have a vent right behind you (top right) that when open uses cab air instead of outside air.

You may even have to take the roof off and clean the overhead unit. if it's clean and working as it should tha fan blows very well, at least it does on mine.

 

[coachgeo]

Sitting for 7.5years tells me odds are good you got some rat nest in places that are blocking air intake and/or outtake. Possibly part of condenser and Radiator along with air filter are must checks.

 

[Daren Todd]

My wife's car would do that for a bit. Ended up being a plugged drain for the condensation catch pan. It would over work the system because it would try to push the air through water. Of course you also had the heater hoses in the same area so the water would get good and hot.

Dug around and finally found the drain for the pan. Apparently the location is one of those super secrets like the code for fort Knox Once I found the condensation drain, I ran a coat hanger up into the hole and got around a gallon of water out AC worked great for a month, then ended up plugging again. So this time I ended up hooking a syphon gun to the drain pipe, and pulling the handle to suck out what ever the blockage was. Ended up being a cricket

 

[BAP]

I had a couple Case/IH tractors that would act like that. It ended up being the heater control valve leaking. It would not shut off completely allowing hot water to flow through causing the A/C to shutdown because of high pressure. We ended up putting a shut off valve in the heater hoses at the engine block and kept it shut off during the summer.

 

[lugbolt]

When that system is working properly, it will blow an automotive a/c system away. Most of them anyway. This is speaking of the vent temperatures specifically. The problem is this. An M9000 has a lot of windows. Windows are very poor insulators when it comes to a/c and heat systems. Thus, when the sun is shining on the tractor, it gets real hot real fast inside the cabin, aka greenhouse. And you're then dependent on the a/c system to "cool" that hot air down to around 20-25 degrees below ambient.

That said, higher highside pressure is usually either excessive oil charge or an obstruction. In this system, it can also be over-charged. 300 psi is probably going to be pretty close on this system and that is with the hood raised and engine at roughly 2200 RPM. Close the hood and the high side pressure should come down some due to air flowing across the condenser core. With the hood up, air comes in around the condensor and through the radiator. Thats why the hoods have "sponges" on them to help direct air through all of the cores (intercooler, radiator, oil cooler, condenser, fuel cooler, etc).

This is one area where it very well could be excessive oil in the system, since I did not see reference to how much oil was removed and then recharged. Perhaps a previous owner could have "recharged" the poorly working a/c system with refrigerant/oil mix?

The problem with putting a higher velocity fan in there is that the more air that moves across the evaporator, the higher the low side pressure will get, and will throw your psi off. This can then become a snowball effect. Put more air across it, psi goes up, so you charge it a little more or a little less, and then you've got a system that is working against itself potentially. If it were mine, I'd pull the cab top off and have a look at the heater box assembly and make sure all of the doors are opening and closing as they should. Also, since it's a tractor that's been around a while, it might be worthwhile to clean the squirrel fan, as they tend to get dirt built up on the vanes and then you'll get low air volume and velocity out of the vents. Also check your vents to make sure they're all sealed up to the ducts.

 

[Tx Jim]

Ditto what lugbolt & BAP stated. I've had manual heater hose cut-off valves on my JD 4255 for yrs because the factory water control valves wouldn't shut 100% of the water going to heater core off.