3.5 SERVICE PRECAUTIONS FOR R134A SYSTEM
LIMIT TIME OF EXPOSURE TO THE ATMOSPHERE
Whenever a sealed system is repaired, do not expose an open line to the atmosphere for more
than 15 minutes. Replacement components will come sealed by either brazing (filter drier) or
plugs (compressor). Do not open the new filter drier to the atmosphere until you are ready to
braze it into place. Before installing a new compressor, pull a plug to be sure the unit is still
pressurized. If no pressure exists, do not use the compressor. If pressure exists, reinstall the plug
to ensure non-contamination during the service procedure.
PLUGGED CAPILLARY TUBE
Moisture or other contaminants in the R134A system can cause the formation of gel-like or
salt-type deposits within the system. This causes capillary tube restrictions which may not be
removed by the flush procedure detailed later. If the restriction cannot be removed from the
capillary tube, evaporator assembly and compressor must be replaced.
SYSTEM FLUSH
Before accessing the sealed system, it is necessary to determine that the problem is actually a
sealed system problem by utilizing a wattmeter, thermometer, visual and touch indicators.
Once it has been determined that the problem is in the sealed system, and diagnosis indicates a
low side leak, plugged capillary tube, or a defective compressor, in addition to the normal repair,
the system must be flushed.
SEALED SYSTEM SUMMARY
A. Recover the refrigerant in the system, if any.
B. Repair the low side leak or replace the evaporator, whichever applies. If the complete low side
is replaced, do not braze the suction line to the compressor until the completion of System Flush
Procedure.
C. Proceed with the following flush procedure.
D. After flushing procedure is completed, continue with the normal sweep and final charging
procedure.
SYSTEM FLUSH PROCEDURE
1. Isolate and flush the condenser
Score and break the discharge line at a convenient location to which the compressor tubing can
be connected later. Attach a process tube adapter to the condenser side of this break. Connect a
quick coupler hand valve to the process adapter. Connect the hose from the charging cylinder to
this valve. This connection will remain in place throughout the flush procedure.
Next, score and break the tube at the outlet of condenser to the input side of the filter drier.
Attach a process tube adapter to the condenser side of this break. Connect a quick coupler hand
valve to this process adapter. Connect the hose from the recovery equipment to this valve. Use
the heater on the charging cylinder to ensure the cylinder pressure to be approximately 30
pounds above room ambient temperature. For example, if room temperature is 70F degrees,
cylinder pressure should be 100 p.s.i.g. Start the recovery system and open the valve at the
process adapter attached to condenser. Open the valve from the charging cylinder and allow 4
ounces of R134A to flow through the condenser and into the recovery system. This process
should take about two minutes. Keep the process adapters and hoses attached at this time.
2. Replace the Filter Drier
Score and break either one of the two inlet lines on the new drier (the other line will remain
sealed until the sweep charge, at which time it will be the process tube). Prepare the drier outlet
side for connection to the capillary tube. The capillary tube should be inserted about 3/4 inch into
the drier to prevent solder alloy from plugging the capillary tube or the capillary tube extending
