ACTION NAPA AUTO Parts - 31

Recovering the entire charge
Blake Gordon

ere in Canada where spring ambient temperatures
are often in the 50°F to 70°F (10°C to 21.1°C)
range, being able to heat the various components
to flash the refrigerant during recovery is a must. With
sealers or stop leak being added to A/C systems, it is important to use a filter to prevent these additives from entering your refrigerant identifier.
To ensure all the refrigerant that is adsorbed in the
compressor lubricant is recovered, you can run the A/C
system for 10 minutes. This will agitate the compressor
oil so the refrigerant will migrate to the condenser where
with heat on the bottom of the condenser will allow for the
recovery of the refrigerant that might be in the residual
oil. Today with more equipment having the dryer built into
the side of the condenser, the ability to heat the dryer is of
utmost importance.
With a manifold gauge set installed on the system, start
the engine and turn on the air conditioning system if possible. If the compressor is not able to be operated due to
a clutch failure, we can still recover the refrigerant from
the compressor by simply heating it with the hot air gun
during the refrigerant recovery process. To prevent the
removal of compressor oil from the AC system, only recover refrigerant vapor from the low pressure side of the
system until system pressure is at least 20psi (137.9kPa)
below the ambient air temperature. At this point, any re-

maining refrigerant in the system will be vapor and you
can begin to recover the remaining refrigerant from the
high side access port. If the A/C system has an access port
on the high side between the compressor and condenser,
you can recover refrigerant right from the start and not
have to wait untill the pressure drops. During the refrigerant recovery stage you must have both the dash and (if
equipped) sleeper fans operating on high blower speed. Be
sure to open the doors so that the air circulates through the
cab. You will know the last bit of refrigerant has boiled off
or changed state in the evaporators when the temperature
of the air leaving the vents is the same as that of the ambient air.
Sometimes it is not possible to heat the bottom of the
condenser. When this is the case, disconnect the compressor clutch wire or remove the clutch coil circuit fuse. You
can then operate the engine and use the engine fan to pull
air through the condenser to boil off the refrigerant.
Once the pressure in the A/C system has dropped to
slightly below zero psi, stop the recovery unit and check
to see if the pressure rises. If it does, this is caused by the
last bit of refrigerant flashing from the oil in the various
components. Start the recovery unit again and recover the
last bit of refrigerant. At this point there is always a small
amount of refrigerant left over in the recovery unit, so also
recover it as well.
When hooking up the refrigerant recovery unit, connect the outlet of the recovery unit to the liquid side of
the recovery tank. The liquid remaining in the tank will
adsorb the refrigrant that is being pumped into the tank
and this helps to keep the tank pressure from rising. After
recovering all the refrigerant, shut off the recovery machine and connect a hose between the recovery machine
and the vapor port on the recovery tank. Start the recovery
machine, open the recovery tank vapor port and the refrigerant in the recovery machine will suddenly move to the
tank, completeing the refrigerant recovery process. ❆

Blake Gordon
Air Conditioning Trainer for
Polar Mobility Research Ltd, Calgary, AB.
You can reach Gordon at
abgordon@telusplanet.net

Spring 2015 * ACTION/NAPA

ACTION NAPA AUTO Parts

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