TM 9-4120-402-14
Table 4-2. Unit Preventive Maintenance Checks and Services (PMCS)
Quarterly Schedule - continued
Item
Item to be
Procedures
Paragraph
Number
Inspected/Serviced
Reference
k. Turn potentiometer TEMPERATURE control knob to fully
WARM (clockwise) position and then turn mode selector
switch to HEAT. After a short delay (approximately five
seconds) the fan should start. Place your hand in air flow
from the conditioned air outlet grille and feel for a
temperature rise. Next, turn potentiometer
TEMPERATURE control knob to fully COOL
(counterclockwise) position. Feel that discharge air
temperature drops to ambient level.
I. Turn potentiometer TEMPERATURE control knob to fully
WARM (clockwise) position, then turn MODE selector
rotary switch to COOL. After a short delay (approximately
five seconds) the fan should start. Hold your hand in air
flow from conditioned air outlet grille; there should be no
change in temperature. Now turn potentiometer
TEMPERATURE control knob to fully COOL
(counterclockwise) position. The fan will stop, after a
short delay (approximately five seconds) the fan and
compressor should start. Feel outlet air temperature
begin to drop. Leave controls in present position and
perform next check.
m. After 15 minutes of operation check the sight glass and
compare refrigerant condition with the color coded
information plate provided.
n. Turn MODE selector rotary switch to OFF/RESET and
observe that all air conditioner functions cease.
o. Set-up the air conditioner for the desired operational
mode.
p. Record performance of quarterly PMCS, including all
corrective actions taken.
NOTE
The potentiometer temperature control has an
effective functional range between 65 and
F
80 (18 and 27 ). In extreme conditions
F
C
C
when ambient air temperature is outside this
range, operation in either HEAT or COOL mode
will vary from that described above.
4-36
