1. With the system evacuated as outlined in Evacuating the System, connect the refrigerant charging hose
to the manifold (refer to Figure 21-11) and purge the charging hose of air.
2. Place the refrigerant container on a scale to observe the amount of refrigerant entering the system.
Open the high pressure valve and add as much refrigerant as possible.
3. Close the high pressure valve, start the engine and operate it at 900 to 1000 RPM.
4. Operate the air conditioner and set controls to maximum cooling.
5. Open the low pressure valve and complete charging the system.
6. Close the low pressure valve after two pounds of refrigerant has been added to the system.
7. With the system still operating, observe the sight glass in the top of the receiver-dehydrator by
removing the plastic plug.
8. The sight glass should be clear of any bubbles or foam. If bubbles or foam are seen passing through
the sight glass, it is an indication of a low refrigerant charge in the system and more refrigerant is required.
This check should be made with OAT of 70°F or higher and with the air conditioner operating.
9. If more refrigerant must be added to the system, open the low pressure valve and increase engine
speed to 2000 RPM and observe the sight glass. After the sight glass has cleared, close the low pressure valve
and observe the pressure gauges. At 1000 RPM the gauge pressure should be 15 to 20 psi on the low side and
150 to 200 on the high side.
—NOTE—
Suspect leaks or an inaccurate scale if two pounds of refrigerant
does not fill the system.
10. Shut off the air conditioning system and airplane engine. Then, remove the charging lines from the
Schrader valves with care due to the refrigerant remaining in the hose.
—NOTE—
A shop cloth should be used to divert escaping refrigerant when
disconnecting the charging hose from the Schrader valve. Recap
the valve.
ADDITION OF PARTIAL CHARGE TO SYSTEM.
It is possible to top off this system with refrigerant by the following method:
1. Remove the access panel at the rear of the cabin.
2. Connect a charging hose to a refrigerant cylinder and also to the Schrader valve fitting on the suction
line. (Refer to Figure 21-11.)
3. Purge the charging hose by allowing a small amount of refrigerant gas to escape at the Schrader valve
fitting.
4. Start the engine and operate at 1000 RPM and turn the air conditioner on maximum cool.
5. Remove the plastic plug from the sight glass in the top of the receiver-dehydrator.
6. With a low refrigerant charge in the system, bubbles will be seen passing through the sight glass when
the system is operating.
7. Open the valve on the refrigerant cylinder.
8. Allow refrigerant to flow into the system until the bubbles disappear from the sight glass.
21-50-15
Page 21-26
December 1, 1978
1G1
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL
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