4940C A/C Issues need help!

[Texasgreen]

Okay heres whats going on with my A/C. The cab will be at ambiant temperature. I can start the tractor up and bring the rpms up to 1800. The cab will cool off nicely. Once the cab cools down, the A/C compressor clutch will start cycling in and out non stop till I depress the A/C button in the cab. I have tried bypassing the low pressure switch and the thermostat controller when the A/C clutch starts cycling in and out and it still does the same, cycling in and out. At this point the cab will start getting warm or back to ambiant temperature.

I cant check the freon levels because I'm not sure what the high and low pressures should be.

Have any ideas whats going on?

 

[Sackett2]

I don't know how a Tractor varies from a car, but when the low pressure is bypassed the clutch should engage all the time. Some cars have a high pressure switch also and most have a AC relay- perhaps it is weak. I found a schamatic...
looking at a schematic, the voltage goes through these components:
A/c switch to the A/c relay- if the relay is switching on and off in time to the compressor, then there could be a switch issue or a bad relay; as it's the only thing that effects the control of the relay. From the relay out it's just a follow the path to find the weak link
A/C relay to the thermostat
Thermostat to the R/D sensor (???) high low pressure switch??
R/D sensor to the compressor.

 

[Texasgreen]

How could I get a copy of the schematic you have. So, is there a relay that powers the A/C clutch on the compressor? The clutch cycles on and off are not in time. What I mean is, when the compressor clutch start intermitting, the intermitting time is not always the same. The compressor will come on and run for 5 seconds and then off for like 3 and than back on for about 15 seconds and then back off for about 5 seconds. The a/c clutch never cycles the same. Keep in mind that the cab is cool now and then thats when the compressor starts cycling and the cab will start to get hot and never cool back down because the compressor is cycling to much at this point.

It sounds to me more and more like a control relay issue.

 

[Sackett2]

It appears that the on/off switch is what controls the relay. I would be looking there.
Basing this on
a: bypassing the low pressure switch doesn't change anything- this rules out 134a pressure as a factor
b: the rapid cycling I don't see anything else that could do that.

I can't send the file until Monday, it's 13 meg's and I run dial up, unless I can figure out how to extract 1 page from a pdf file

Message tractorbarry or Jdeerekid and ask them for a manual for your tractor

 

[Gator6x4]

If I was going to attempt a self repair I would obtain some indepth information on High and Low side gauge readings. I Would also obtain some type schematic on the system used by Montana. Surely there is a Montana Dealer in Texas that will either provide this information free or at least for a fee. Operating a tractor without AC with a cab is like working while setting in an oven. An improper repair to the AC system on a tractor or in an automobile can get expensive fast. I have provided a link to three locations that provides basic information on how an automotive AC works and the various components. I have seen automobiles with AC exhibit the same symptoms you described with a defective Thermal Expansion Valve or Orifice Tube. If you have an independent AC repair facility for automobiles in your area discuss the problems experienced with the service manager or one of the techs.


Automotive Air Conditioning Systems

Air Conditioning - How Does A/C Work - Automotive Air Conditioning Components Description

How to Fix Your Car's Air Conditioner - wikiHow

 

[blueriver]

The screen and the radiator are probably plugged with dust and crud ... blow them out with air ....

 

[trac]

I am agreeing with blueriver. I think you are having a problem with the high pressure side. If the pressure reaches a certain level, it with shut the compressor down until it lowers. I would say that the condenser and radiator on the tractor needs cleaning out. Being that we don't knows the hours on the unit,(assuming their low). These korean tractors don't have alot of issues with air conditioning. trac

 

[Gator6x4]

I am agreeing with blueriver. I think you are having a problem with the high pressure side. If the pressure reaches a certain level, it with shut the compressor down until it lowers. I would say that the condenser and radiator on the tractor needs cleaning out. Being that we don't knows the hours on the unit,(assuming their low). These korean tractors don't have alot of issues with air conditioning. trac

All automobile AC units that I have seen that are having a high pressure problem are very easy to detect. The belt driving the AC unit will slip on the AC clutch, make a high note squealing noise and smoke will emit from the belt. The belt will eventually break. A lot of vehicle owners also complain of smelling burnt rubber when the AC is being operated.

 

[Texasgreen]

Problem is solved. Thanks for all of the help! It was the clutch on the a/c compressor. The clutch magnet would get hot and start kicking in and out. I used a volts meter and probed the plug going to the A/C clutch when it would start cycling. The voltage would remain steady. I took the compressor to a auto a/c shop and they were able to test the clutch magnet and it would start cycling on their bench test. They ordered me a new compressor. When it gets here well pull a good vacuum on the system and recharge it.