What a time for the A/C to fail

[sunnyside360]

He's not that far off with a 92 degree ambient.

Also, the engine was a little warmer than ambient 92 deg from running it a few hrs earlier. Will check static pressures again when cooler.

 

[sunnyside360]

BTW a good test for the clutch gap is to put the AC on MAX (so you know it should be engaging) and then whack the clutch with a broom handle or screwdriver handle (like pushing it in). If it grabs even for a second or two, your clutch gap is too wide and the coil can't pull it in. Adjust the gap. If not you have other issues - start looking for voltage on the coil connector for one. Then you can jumper the LP and HP switch connectors to see if they are faulty.

Will give this a try this AM. I just got off the phone with the Kubota dealer service guy and went thru the whole issue with him. He suggested removing the roof and checking for blockages there prior to hauling it in for service. He also said they get very very few calls on Kubota A/C system failures so he couldn't point to a common failure mechanism (good news). He said any problems they do see are almost always a result of debris/blockages in the air flow.
In this case though, it seems the compressor should engage and run for a short time until the pressures rise if there are blockages in the roof area.

 

[dstig1]

Also, the engine was a little warmer than ambient 92 deg from running it a few hrs earlier. Will check static pressures again when cooler.

Yeah with ambient at 92 and the engine being warm, you are probably fine then at 125, but the extra freon you added should have overcharged it unless it was low...

And yeah your problem sounds more electrical or mechanical, not airflow-restricted.

 

[sunnyside360]

Just got done doing some tests. With ambient temperature at 86 deg, static pressure on both HI and LO side was 90 psi.

Put the gauges on and started the tractor and let run with following results.

Time...........LO.......HI.......Comments

9:59AM......90.......90.......measured static, turned A/C & fan on max
10:00AM.....28.......300......clutch engaged, cold air at vents
10:05.........28.......310......clutch engaged, cold air at vents
10:10.........28.......320......water drip profusely from vent hoses
10:14.........27.......325......clutch disengaged, compressor stopped
10:16.........74.......125......no compressor op
10:18.........88.......110......no compressor op
10:20.........100.....100.......bumped clutch front with handle, no op
10:30.........104.....105.......pressures stable, still no compressor op
10:35.........104.....105.......zero volts at clutch, still no compressor op

Going out on a limb here, it looks like the problem is either in the wiring to compressor or cutout switches. Also, looks like too much refrigerant with HI pressure going to and settling around 325 deg. According to info found online HI pressure should be settling around 200 deg.
I'm totally new at this. Am I going down the correct path and making the right conclusions?

 

[dstig1]

My Ford Explorer AC tables show 150-240psi as the normal high side pressures at that ambient temp, which is pretty typical. Your high pressure switch could be cutting out for that reason, which could be unrelated to the problem you started with. That could be the overcharge showing up.

Try jumpering the low cutout switch connector. If the clutch kicks in, you have your culprit. If not, try jumpering the high side switch connector, but watch the pressures to be sure it doesn't spike too high as a result of overcharging. Safety glasses are important when doing this work. You can check for voltage at those pressure switch connectors too, if you need to dig deeper.

 

[sunnyside360]

Try jumpering the low cutout switch connector. If the clutch kicks in, you have your culprit. If not, try jumpering the high side switch connector, but watch the pressures to be sure it doesn't spike too high as a result of overcharging. Safety glasses are important when doing this work. You can check for voltage at those pressure switch connectors too, if you need to dig deeper.

Sounds like a good idea. I will try your suggestions. Not sure where these LO and HI pressure switches are located........ they may be in the roof enclosure.
Do you happen to know? Also, to replace a switch, does the system have to be purged and recharged?

 

[dstig1]

I can't say that I have ever seen a Kubota system - so this is general car AC system advice. The low pressure switch should be near the evaporator - often they are on the receiver/drier cannister. The HP switch is likely on or near the compressor. I would look for something with a plug and 2 small wires coming out of it. Trace the lines and you should find them. On car AC systems, there is a Schrader valve behind the pressure switches so that the system does not need to be dumped to change the valves. I would guess this is the same, but I cannot be certain on that having never seen it. If you try removing them, make sure you have a rag around them and wear gloves and safety glasses. At the minimum there will be a spurt of freon. Any more than that and you will know there is a problem or no valve. Can you call the Kubota tech at the dealer and ask him? He should know how it is set up for sure. I would bet there is a valve under there, but it isn't me working on it, so do what feels safe to you. A blast of freon will cause instant frostbite or blindness if it hits your eyes. You want to be careful here...

System off and stabilized at normal pressure for this work!

-Dave

 

[sunnyside360]

Well, I ordered the shop manuals today and made an appointment for mobile A/C repair at my house on Friday. It was going to be around $300 for transportation to take the tractor to a repair shop (round trip). I've taken the problem about as far as I can with the knowledge I have. I will post the repair info when it is fixed.

Many thanks to all who helped.

 

[timswi]

Well, I ordered the shop manuals today and made an appointment for mobile A/C repair at my house on Friday. It was going to be around $300 for transportation to take the tractor to a repair shop (round trip). I've taken the problem about as far as I can with the knowledge I have. I will post the repair info when it is fixed.

Many thanks to all who helped.

Keep us informed as to what the issue turns out to be.

I have also heard that the Kubota A/C is pretty much bullet proof as far as these things go. So I am curious.

(I have the same system in my RTV).

 

[DiezNutz]

Reminds me of when our house A/C died in the middle of July 2 years ago. Though I have to admit sunnyside, when it hits 104 here today and I go to pull my non-cab/non-AC tractor out of the ~130 degree garage later, I'd be finding it real hard to feel for anybody with a nice cab & A/C.

But as it is, now that you've been kicked down here with the rest of us peasants haha, I genuinely feel bad for you. That is, until you get it fixed. Which I hope is soon. Good luck.

-DN