4440 Air Conditioning

AC was working fine then I heard the belt start to slip. Checked the belt tesion but it was tight. I turned it off for a while and then back on and it cooled fine for a short period of time then the belt started to smoke. Turned it off for a while and then back on. Compressor turns slower than tractor RPM. Do I have a clutch problem or a compressor problem? Any help would be appreciated.

It could be a little of both, and your evaporator could be freezeing over causeing high pressure makeing the pump turn harder, a plugged over (outside dirt) evaporator will cause this along with a dirty filter, if you pull the filter down you can peek up in there to see if it's frosty when the belt starts to slip, if it's real dirty you will need to lift the top off and blow it out good, check the drain tubes good while your in there.

First of all, take a look at the belt and the pulleys to see if the combination of a worn belt and worn pulleys is causing the belt to bottom in the grooves and slip.

If they're OK, you need to hook up a gauge set and have a look at the high side and low side pressures to make a diagnosis.

A blocked or frozen evaporator (coil mounted in the cab) will cause a low suction pressure rather than a high discharge pressure. A blocked condensor (coil mounted by the radiator) will cause a high discharge pressure, but I have seen some extremely high discharge pressures and still not cause the belt to slip.

You need to find out the pressures first, but if I had to guess, I would say that you have lost a bearing in the clutch or you've seized the compressor. If the pulley will not turn with the clutch de-energized, you probably need a a new clutch assembly. If the pulley turns but stops when the clutch is energized, then you most likely need a compressor. The major cause of compressor failure is the return of liquid refrigerant to the compressor because of low air flow across the evaporator. (liquid refigerant is a solvent and compressor bearings and wear surfaces hate that)

Of course, this is all assuming that you do not have a plugged drier or expansion valve, which would look like an undercharge when the gauges are put on, and then you added more and more refirgerant until you overcharged the system. That too, would cause the belt to slip.