Henry Guenter, is a former service manager for Massey Ferguson. He has compiled information on air conditioning and what to check when it fails.
Air conditioning is used on many machines, yet there are things about it that baffle us.
Here is how it works.
Liquid is turned into gas by dropping the pressure. A law of physics states that when pressure is lowered on a liquid, its boiling point is also lowered. So when the liquid wants to boil at a lower temperature, it still needs heat to do this. It gets the heat out of the warm air from the cab that we blow across the evaporator.
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As this gas moves by a hose to the condenser, it raises the pressure again at the condenser, so the gas wants to become a liquid again.
To do this it has to lose a lot of the heat that it picked up inside the cab.
This results in a transfer of heat from inside the cab to outside.
A typical maintenance scenario occurs when the operator freezes up the evaporator core in the cab.
He turns on the air conditioning in the morning. He has already changed his cultivator shovels and his boss has been out to see what is taking him so long to get going. In addition, the beer he had the night before makes him even more hot and sweaty.
He turns the air conditioning on high, with air blowing on his face full blast.
Pretty soon this blast of air is uncomfortable so he turns the air fan down but leaves the temperature cold. This is a perfect setup for failure.
The air conditioner lacks enough air to draw out heat, so it takes the rest of the heat from the moisture that collects on the evaporator. This condensed water turns to ice. Pretty soon the evaporator is a solid chunk of ice and the system fails.
Our operator phones the dealer and he gets there and puts on the gauges. By that time the ice has melted and it all works well and the farmer is out the service call fee.
Next morning the same thing happens. The operator turns off the AC when it quits and works the rest of the morning without it. Whenhis boss shows up he asks the operator why his cab is so hot. He tells him the AC doesn’t work again, but when the boss climbs in, everything is working fine.
By this time one of them should have figured out that when the fan is turned down, the temperature must be turned up.
Allowing the evaporator to plug with dirt will produce a similar result, but this time the AC won’t come back by waiting.
It’s a different story when the condenser in front of the radiator becomes plugged. The lines get hotter until a component fails, which can cause real damage to the system.
Remember, the heat that was collected in the cab is supposed to be eliminated at this stage, but what happens if it isn’t? It’s still in the system and keeps building until something fails.
By the way, it is a good idea to remove the compressor and set it on its pulley for long storage. It keeps the seal wet.
Here are some quick checks to help find out what is wrong if the AC system is causing trouble:
- Does the compressor come on (the motor can be heard to lug down a little) and turn off regularly? It’s good if it does. If it runs constantly, the condenser core might be plugged or the AC might be low on gas. If it does not engage at all, the clutch is probably burned out.
- Find a small window some place in the system, probably on top of the dryer. When the compressor comes on, a surge of bubbles should be visible for a fraction of a second and then it should run clear, continuously. No bubbles either mean there is no coolant flowingin the system or it has been overfilled.
Producers can repair their air conditioners if they have the proper tools and if they know what they are doing. If they don’t, this is as far as they should go.
Perform these simple checks before calling the dealer.
He will probably ask the same questions.
