Air Conditioners.

TM 55-1905-223-24-17

(4) V-belt Drives.

(a) A noisy V-belt indicates the need for attention. However, it is normal for belts to squeal slightly

at startup. V-belt noise can be caused by the slapping of the belts against the drive guard or

other obstruction. Check for an improperly installed guard, loose belts, buildup of foreign

material in the sheave grooves, or excessive vibration. The cause of excessive vibration

should be determined and corrected.

(b) Ideal V-belt tension is the tension at which the belt will not slip under peak load conditions.

Overtensioning shortens belt and bearing life. Belts should be free from foreign material which

may cause slipping. Do not use belt dressings.

rim can damage belts. Dust, oil, and other foreign matter can lead to pitting and rust, and

should be avoided as much as possible. Badly worn grooves or a shiny groove bottom

indicates that either the sheave, the belt, or both are badly worn. Sheaves that are not aligned

properly cause excessive belt wear and sheave wear.

(5) Motor and Fan Bearings.

(a) The most frequent cause of bearing failure is not greasing often enough, using an excessive

quantity of grease, or using incompatible greases (LO 55-1905-223-12).

(b) Excessive vibration, especially if the bearing is not rotating, will also cause bearings to fail.

Bearings must also be protected from water and moisture to avoid internal corrosion.

Air Conditioners.

(1) When it is necessary to remove or add oil to a compressor, remember the following:

(a) Never save compressor oil for re-use.

(b) Never add compressor oil that has come in contact with the atmosphere.

(2) When troubleshooting the self-contained units (A/C-1 and 3) it will be necessary to determine

operating pressures by using a portable gauge manifold. There are no fixed gauges installed in

these systems. Also, use a portable gauge manifold on the accommodations unit (A/C-2) when a

defective gauge is suspected on the installed fixed manifold.

(3) Time guard circuit will delay re-starting the compressor for 5 minutes after it has been shut down

for any reason.

2-14. Troubleshooting Electrical Voltages and Components. The following information is to assist maintenance

personnel when troubleshooting voltages and electrical components within the HVAC system.

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