Cadillac 60 Series 1963 Shop Manual page 397

13-16
HEATING AND AIR CONDITIONING
Fig. 13-14 Evaporator Assembly
case, Fig. 13-14, just below the suction throttling
valve. An expansion valve is also used on the
rear evaporator assembly on 75 series cars.
The expansion valve can be described as a
temperature and pressure sensitive refrigerant
control valve. At the orifice (or restriction) of
the valve, high pressure liquid refrigerant changes
to a low pressure liquid and enters the cooling
coil.
The expansion valve regulates the flow of re-
frigerant through the cooling core in the evapora-
tor. It is pre-set at the factory and is not
adjustable.
Oil Bleed Line
The oil bleed line runs from the bottom tank of
the evaporator core and connects to the outlet
side of the suction throttling valve.
This line is used in the system to protect the
compressor during periods of low refrigerant
charge. Under normal charge conditions, this
line has no active use, as the compressor obtains
an adequate oil supply.
With a partially depleted refrigerant charge,
any excess oil and refrigerant mixture will flow
from the bottom tank of the evaporator core
through the oil bleed line to the compressor out-
let on the suction throttling valve. The oil is then
carried to the compressor through the low pres-
sure line. This oil flow prevents any oil defi-
ciencies in the compressor that could arise during
periods of low refrigerant charge.
CAUTION: During periods of zero charge,
no refrigerant: is available to carry oil back to
the compressor. Do not operate a completely
discharged system or compressor seizure
might occur.
A check valve is used in the oil bleed line at
the port connection on the suction throttling valve.
This check valve opens at 5 psi differential pres-
sure, and is fully open when the differential pres-
sure exceeds 12 psi. Below the 5 psi differential,
the check valve is closed to prevent capacity loss.
This feature prevents refrigerant by-passing the
evaporator at traffic conditions when cooling de-
mands are greatest.
Condenser
The condenser is an aluminum heat transfer
unit similar in appearance to the radiator, and
located in front of the radiator assembly.
The function of the condenser is to transfer
the heat picked up by the refrigerant to the air
stream passing through the condenser core. In
the condenser, high temperature vapor is cooled
by outside air and converted back to a liquid.
This liquid refrigerant is then collected in the
dehydrator-receiver and is available for further
use in the cooling coil when required.
Dehydrator-Receiver
The dehydrator-receiver is an aluminum tank
3 inches in diameter, having a compartment filled
with a moisture-absorbing material or desiccant.
It is located on the right front side of the con-
denser. The sight glass is an integral part of
this assembly.
The receiver acts as a reservoir for refriger-
ant and the desiccant removes moisture that may
have accidentally entered the system.
Evaporator
The evaporator is located on the right hand side
of the cowl, Fig. 13-14. In addition to a front
evaporator, 75 series cars have a rear evapora-
tor, which is mounted in the luggage compartment
below the package shelf.
The evaporator case is constructed of plastic
and contains an aluminum cooling core. The core
is the container for the liquid refrigerant, so
designed that it can readily absorb heat from the
surrounding air. It is similar in construction to
the car radiator.
The core is made of aluminum tubes that pick
up heat from the air and transfer this heat to the
refrigerant. The tubes are spaced closely toge-
ther to provide maximum surface area.