What a time for the A/C to fail

[EE_Bota]

I have a 5 yr old Kubota M8200 cab tractor with 400 hrs and the A/C just started failing yesterday morning. At first, when the compressor would kick in, the air would be really cold. When it would eventually turn off, it would never come back on unless I turn off the A/C switch and then turn it back on. After a couple of hrs of mowing, the system died altogether. What a time for it to go on the blink -- supposed to be in mid 90's all week here in Central Pa. I keep the tractor maintained according to the service schedule and it's been "rock solid" up until yesterday.
Anyone have any ideas as to what the problem may be?

Having read the thread to this point, my suggestion is to be sure the A/C compressor clutch is engaging. It would be very easy to turn an electrical problem into a refrigeration problem, and that is to be avoided.

It was mentioned earlier that a sensor could be keeping the clutch from engaging. This is very true. But so could a loose wire. But even if it were a sensor, it would be valuable to know which sensor, and what it is designed to sense?

 

[RickB]

Check the condenser coil and the area between the condenser coil and radiator for accumulated debris blocking airflow. Poor condenser airflow= higher than normal highside pressures= high pressure switch opens and no cold air.

 

[sunnyside360]

Check the condenser coil and the area between the condenser coil and radiator for accumulated debris blocking airflow. Poor condenser airflow= higher than normal highside pressures= high pressure switch opens and no cold air.

I removed/cleaned the screens and blew out the radiator and coils in front of the radiator. There was very little debris in there -- no joy. I'm going to get the VOM out tomorrow and check the voltage at the compressor since it is not running and trace it back. Also plan to get a set of gauges to check the refrigeration unit according to info here Troubleshoot Automotive Air Conditioning Problems

I never got a shop manual because the darn tractor never broke but now may be the time to get one.

 

[number two]

Refering to post #5,the system blows cold air instantly upon clutch engagement-sounds like the problem lies with the clutch not engaging.Maybe apply 12 volts to the compressor clutch and see if the clutch engages and makes cold air.If the clutch engages and makes cold air,the A/C system is good to go and purchase of guage set is not needed at this time.
This indicates an electrical problem-something is not supplying voltage to the clutch.This is where the shop manual would be helpful,maybe a better purchase at this time than a guage set.I was reading up on the A/C system on our B3030 cab model awhile back and the clutch is controlled by an evaporator temp switch.Your tractor may be different.Will love to hear your outcome.Good Luck.

 

[sunnyside360]

Refering to post #5,the system blows cold air instantly upon clutch engagement-sounds like the problem lies with the clutch not engaging.Maybe apply 12 volts to the compressor clutch and see if the clutch engages and makes cold air.If the clutch engages and makes cold air,the A/C system is good to go and purchase of guage set is not needed at this time.
This indicates an electrical problem-something is not supplying voltage to the clutch.This is where the shop manual would be helpful,maybe a better purchase at this time than a guage set.I was reading up on the A/C system on our B3030 cab model awhile back and the clutch is controlled by an evaporator temp switch.Your tractor may be different.Will love to hear your outcome.Good Luck.

My line of thinking is actually very similar to yours. But, I'm somewhat reluctant to throw 12 volts on the compressor w/o putting the gauges on because I already put a can of refrigerant in the system and the pressures may be very high.
I put out some email inquiries for a service manual and am waiting for responses.

 

[Willl]

I already put a can of refrigerant in the system

Before it died completely ?

 

[TripleR]

My line of thinking is actually very similar to yours. But, I'm somewhat reluctant to throw 12 volts on the compressor w/o putting the gauges on because I already put a can of refrigerant in the system and the pressures may be very high.
I put out some email inquiries for a service manual and am waiting for responses.

Did you check the sight glass before adding refrigerant?

 

[sunnyside360]

Before it died completely ?

Yes. I believe the compressor must be engaged/running while adding refrigerant.

 

[sunnyside360]

Did you check the sight glass before adding refrigerant?

Yes, I checked the sight glass and saw nothing before or after adding refrigerant.

 

[TripleR]

Yes, I checked the sight glass and saw nothing before or after adding refrigerant.

Lots of bubbles will indicate low refrigerant levels.

Before I get jumped on, I know all about the need for gauges etc, but people still charge their own systems without them, no matter what anyone says. Looking at the sight glass is a good first indicator of "possible" problems as indicated in my manual and from past experience.