TM 9-4120-357-14
1. Place the refrigerant cylinder on a scale of sufficient capacity, with the shutoff valve down, or suspend the cylin-
der from a spring scale or beam scale, with the valve end down.
NOTE
If cylinder is equipped with both liquid and gas (vapor) valves, connect the line to the
liquid valve.
2. Weigh the cylinder, and record the weight.
3. Open the discharge line service valve, and slightly open the refrigerant cylinder shutoff valve. Liquid refrigerant
will be sucked into the refrigeration system rapidly at first, then more slowly as pressures begin to equalize. When 25
pounds (11.4 KG) of refrigerant have flowed into the refrigeration system, as indicated by the scale, close the discharge
line service valve and the cylinder shutoff valve.
WARNING
Hearing protection must be worn when maintenance is performed while air conditioner is
in operation. Failure to heed this warning can result in hearing loss or injury.
CAUTION
Connect power to unit as soon as possible after charging or any period when power has
been disconnected. Allow heater time to vaporize refrigerant in compressor before opera-
tion in COOL mode. If knocking or pounding is hear at start of COOL mode, turn selector
switch to OFF or VENTILATE at once and allow additional warm up time.
(e) With power connected to the air conditioner, turn the mode selector switch to cool, and turn the temperature
control thermostat to maximum decrease position. Temporarily prop front access panel across the opening. With com-
pressor operating, observe the sight-glass liquid indicator. If bubbles or milkiness appear, top off the refrigerant charge
as follows:
1. Connect a cylinder of refrigerant, R22, loosely to the gage port of the suction line service valve, and open the
cylinder shutoff valve for a few seconds to purge air from the line. Tighten the connection. Leave the cylinder up-right,
or connect line to the vapor valve.
2. With the air conditioner compressor operating, open the suction line service valve and the cylinder shutoff valve
to charge refrigerant gas into the system, while observing the sight-glass liquid indicator.
3. When liquid in the sight-glass indicator runs clear and free of bubbles, close the suction line service valve and
the cylinder shutoff valve.
4. Disconnect the refrigerant cylinder, and replace caps on both service valves.
g. Final Assembly. Replace panels and grilles on the air conditioner as follows:
(1) Position the front access panel on the unit by placing its lower edge behind the step in the front of the base plate
and pushing into position, secure with four panel fastener screws.
(2) Position the evaporator intake grilles on
the air conditioner. Secure them with 12
screws and washers each.
5-21. Pressure Relief Valve.
a. Access. The pressure relief valve is located behind the junction box in the upper part of the lower compartment.
To obtain access to the pressure relief valve, proceed as follows:
(1) Unscrew four panel fastener screws in the front access panel. Remove the panel.
WARNING
Disconnect power input cable from the air conditioner before doing maintenance work on
the unit. The voltage used can be lethal.
(2) Disconnect all wiring harness plugs from the junction box and control panel assembly.
5-35