Help troubleshoot a/c on Kubota

[Mseriesfreak]

I have a M105X that has unsatisfactory a/c operation.First off i have checked the condenser for dirt and dust,inside and outside cab filters.Yesterday i had a 90 degree ambient temp.with humidity here in north Alabama with the doors open blower on high i had pressure readings of 15 PSI on suction 260PSI on discharge,the compressor would stay on 26 seconds and the go off for 7 seconds i had 55 degree air at the vents.The suction line at the compressor never sweats it is only cool to the touch.I closed the doors and the compressor came on for 14 seconds and went off for 6 seconds.I still had 55 degree air at the vents.I am almost convinced it is the expansion valve bad.What do you think?How can i check it?

 

[wushaw]

Last time I troubleshot A/C systems was in the days of R-12. I don't know if the R-134 pressures are different but if it was R-12 it looks like your pressures are a little low indicating low freon and the low pressure switch on the dryer is kicking off.

 

[mit]

it surely sounds like the gas is low causing the compressor to cycle on and off with very little cooling.

 

[shaley]

Low Freon, That's my vote. If that doesn't fix it then its the X valve.

 

[Chuck K.]

If it has a sight glass on the liquid line it sure is nice to determine if the system is under charged by the presence of bubbles. Based on your pressures readings I believe the other posts are correct.

 

[DieselPower]

I would agree with the others, going by the pressure it looks to be a little low on refrigerant.

 

[BobRip]

I agree, low freon. Look for a fitting or other area that is oily looking. This is probably your leak. The leak could be at the shaft seal on the compressor or in the condensor or evaporator. Refiling with freon may fix it for a while or even a long time.

 

[skipmarcy]

If your system is R134a, the pressures are too low. Suction side at 90 ambient with some good southern humidity should run around 25 - 28 psi and head pressure will go upwards of 300+ psi . R134a is an extremely dense refrigerant and does not lend to "topping up" like the old R12 - ideally you should evacuate and precisely weigh the recharge, but if you're careful you might hit the right charge by adding some. Overcharging an R134a system by only a few ounces will cut cooling in half in hot weather. Any automotive type a/c system that can drop ambient air temp. by 30 - 35 degrees at high fan is considered to be in operating range, airflow of course is a critical factor on this too - at the condenser and evaporator both. If after adding maybe 4 ounces (+/-) your pressures don't come up, you can start suspecting the expansion valve being stuck open.