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TM 55-1905-220-14-8
4-29. AIR CONDITIONING SYSTEM - MAINTENANCE INSTRUCTIONS (Continued).
return to compressor or excessive oil circulation in system.  Refer to volume 3.
Take
corrective action promptly if crankcase temperature is abnormal.
(b) Discharge Temperature.
With the compressor warmed up and operating normally, the discharge gas temperature
should not exceed 240 (115.6 ). If it should, bypass the heat interchanger.
F
C
(c) Head and Back Pressure.
Head and back pressures are basic indicators of system operation. Refer to Volume 3.
Head and back pressures will also show whether the compressor suction and discharge
valves are operating correctly. If suction pressure is abnormally high and discharge pressure
abnormally low, either the suction or discharge valves may be leaking. Leaky valves will
usually result in lack of refrigeration and long running time.
(3) Compressor Noises.
(a) Compressor noises may be due to vibration because of improper mounting, or improperly
aligned, loose or worn compressor drive. These and other possible sources of compressor
noises are listed with corresponding remedies in Volume 3.
(b) In some cases, noise may seem to come from the compressor but originate elsewhere in the
system. Other possible sources of system noises are given in Volume 3.
(c) When investigating noisy operation, keep in mind that the operation of the capacity control
system will change the characteristic operating sound level of the compressor.
(4) Adjustment of Belt Drives.
(a) After a period of operation, new V-belts will stretch and slip if not kept tight. If the flywheel or
motor pulley appears to be warm, the belts are probably slipping. Slippage will cause loss of
speed to the compressor and excessive belt wear. Keep all belts at proper tension or they
will soon be ruined.
(b) Belts can be adjusted by moving the universal adjustable motor rails. V-belts when properly
adjusted can be depressed about 1/2 to 3/4 inch (1.27 to 1.9 cm) with the pressure of one
finger. Do not tighten belts too much. Very tight belts will cause excessive wear of both the
belts and main bearings of the motor and compressor. In extreme cases, tight belts may
cause shaft seal leaks.
(c) Fan belts should be checked and adjusted for proper tension in the same manner as above.
4-903


 


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