What a time for the A/C to fail

[sunnyside360]

Had about an hour this morning to work so I removed the roof -- very simple, just remove 10 long screws from inside the cab. Only took about 15 minutes and my wife helped lift the roof off the cab. It is much lighter than the roof on my John Deere cab tractor. I immediately found the LP cutout switch. Could not find the HP switch but suspect it is inside the plastic enclosure where the condenser is located. The LP switch does not look like the schrader valve on my GMC Sierra truck so don't think I will mess with it until the service tech gets here Friday morning. I may check the voltage at the LP switch when I have time later today. Dang doctor appointments always seem to come at the wrong time.

 

[sunnyside360]

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).

My Kubota A/C system has been great up to now. With 400 hrs on the meter, I'd say about half of those are with running the A/C so in my opinion it should last a lot longer. Some folks put that many hours on their machine in one year. The tractor could almost pass as NEW. Heck I took the roof off this morning and it looks bran spanking new in there. Thought I'd find a lot of debris but not so.

 

[lawn_king]

I took my roof off this spring to replace the cheap factory speakers with a nice set of kickers, i think it was hey jude that blew them! All i could think of, looking at the tractor with the roof off, was the quick shot of darth vader with his helmet off, in the empire strkes back.

 

[Willl]

Just some FYI, 325psi is a common setting for a 134a HP cutout.

 

[sunnyside360]

I visited the Kubota dealer today to peruse the M8200 Shop Manual for info on the A/C system. With engine at 1500 rpm, Max cooling and Max fan speed, the LP operating range for cycling between 86 and 95 deg F ambient temperature is 21 to 28 psi. The corresponding HP range is 185 to 242 psi. Manual says the system has a "dual type" pressure switch ----- LP switch turns off at less than 28.4 psi and HP switch turns off at more than 455 psi (not exactly sure what that means).

It also stated the failure mechanism for my problem could be magnetic clutch, compressor, thermostat, pressure switch, expansion valve, A/C switch, or clogged condenser.

There is too much R134a refrigerant in the system for sure. I'm thinking I could put the gauges on when the weather/temp is 95 deg and release refrigerant on the low side until HP is around 240 psi. Can someone confirm this would work? Thanks.

 

[dstig1]

Expansion valves are pretty bullet proof - unless the compressor grenades and fills the system with debris (aka Black Death). But then you have a total system rebuild. Since yours blows nice and cold when working, that isn't it.

Not sure what they mean by Tstat - is there one on the evap or in the cabin for the HVAC? Obviously it is not the engine Tstat...

Checking for voltage at the clutch would be wise. If you don't see it when it should be engaged, then odds are it's electrical. In fact, as I look back through the thread, here's the key from an earlier post of yours:

10:35.........104.....105.......zero volts at clutch, still no compressor op

Zero volts at clutch means the system is not telling the coil to energize. The electricals are really butt-simple here. Selector switch to LP & HP sensor and maybe some tie-in to an engine computer. Work your way back from the clutch and forward from the switch. Look for voltage at any connection you can find and wiggle wires and connectors. It might just be a bad connection or internally broken wire in the wiring loom. This is where jumpering the LP switch is often done to see if the LP switch is bad.

The "dual type switch" I think is just lousy Japanese translation. I believe they just mean it has both LP & HP switches, which is typical.

Now as for letting freon out. You will have to let it out via the gage set, but you need to be REALLY CAREFUL here as any freon contact with skin can/will cause near instant frostbite. Long sleeves, gloves, safety glasses and some way to activate the outlet like a screwdriver tip. That will depend on how your gage set operates for how you can let it escape. System off and stabilized at ambient pressure too. You will have to blow out a lot to get rid of a full can that you added...The system may only take 2 or 3 cans for full charge and you added one more to that. That's a large percentage of the total charge. The other way to deal with this is to have the tech hook it up to a recovery machine, suck it all out, vacuum the system down and then add back the correct amount. If you have a guy coming, you may want to let him do it that way.

 

[doall]

probably shouldn't announce releasing freon to atmosphere.:thumbsup:

 

[dstig1]

Why? You have a thing for Polar Bears or something?:laughing:

Yeah, you "shouldn't" do it, but it's done all the time....Intentionally or not. That was one of the reasons they switched from R12 to R134a - far less damaging to the ozone.

 

[KennyV]

I will have to agree with Dave... sounds like he has you on the right track...
reading through this I figure you are a can over full... I would sure think all indications are not the correct amount of air flow through the condenser... Will be interesting to see what you find out.

Kubota AC are great I have over 1000 hrs on my L4200 with no problems... except one that I accidentally encountered and fixed without realizing it was a problem...
While you have the roof off, Is there any insulation on the inside of the roof?
My roof did not have any so while I had it off, changing speakers, I stuck a sheet of the foil backed bubble wrap against the underside... After doing that I can run on Low or medium cool and it gets very cold inside the cab, have not used hi setting except when first starting out, made a huge difference. You might consider doing the same after you get your problem figured out... KennyV

 

[lawn_king]

Check the drain hose on the unit as well, i had to pull my roof to reattach it, as it vibrated loose and the unit was draining into the cab.