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24-28
AIR CONDITIONING
hoses
are
identified by yellow color coding:
a
yellow
stripe on the hoses and two yellow dots of paint on
the body of the thermostat. Also remove the large
diameter vacuum source hose from the other ther-
mostat and plug the end of it to prevent any air from
entering. This hose has a green stripe.
Thermostut
M
id-Post ion Setting
Put the temperature selector lever in the
"Off'
po-
sition, then move it slowly toward the center of its
slot. Stop when the vertical line on the cam lever arm
is aligned with the raised vertical line on the end of
the valve body (Fig.
34).
If you over-shoot the mark,
don't move the lever directly back to the proper set-
ting. Instead, move the temperature selector lever
back to the
"Off'
position and start over. The test
which follows
is
based on having the thermostat cam
precisely in its mid-position point.
Calibrution Test
When the heater stat is set precisely on the mid-
position and the air temperature at the upper grille
outlet is stabilized, read the thermometer and vacu-
um gauge. For any given temperature, the vacuum
should be within the limits shown on the following
chart.
Check valve test.
To be sure that the vacuum check
valve in the thermostatic valve assembly is working
correctly, disconnect the source hose from the vacu-
um pump. This will release all vacuum in the vacuum
source lines up-stream from the valve. If the vacuum
gauge reading drops less than one inch in one minute,
the check valve is satisfactory.
AIR-CONDITIONING THERMOSTATIC
VALVE TEST (Fig. 35)
The air-conditioning thermostatic valve is the right
I
Fig.
34-Jhermostat Mid-Position
Fig. 35-Air-conditioning
Thermostatic Valve Test
hand valve. The valve and its hoses are identified by
green color coding-green
stripes on the hoses and
two green paint dots on the valve itself. To test this
valve, attach the test hose from the vacuum gauge
to the outlet fitting at the right-hand side of the
valve. Disconnect the vacuum source hose from the
heater stat and plug the hose. Connect the large-di-
ameter vacuum source hose with the green stripe to
the air-conditioning thermostatic valve.
Repeat the thermostat mid-position setting and then
read the thermometer and vacuum gauge again. Refer
to the following chart for vacuum limits for the air-
conditioning thermostat calibration test. Then test the
vacuum check valve as described for the heater stat.
THERMOSTATIC VALVE REPLACEMENT
The two thermostatic valves are serviced only as an
assembly, complete with the mounting plate.
So
if
either stat doesn't test out okay, replace the assembly.
Don't attempt to adjust or replace individual stats.
Remember to disconnect the battery and remove the
fuse block before you remove the stats. To remove
the assembly, remove only the six screws around the
perimeter of the mounting plate; never disturb the
four screws that hold the individual thermostatic
valves to the mounting plate. Tightening or loosening
them, even very slightly, may upset the calibration of
the stat. To remove or install the assembly, roll it in
or out of the evaporator housing from the bottom
of the mounting plate. This will avoid damage to the
thermostatic springs and cam followers.
When you're handling the assembly, be careful not
to damage the bimetal thermostatic springs in any
way. Avoid touching the springs since contamination
could cause corrosion and affect calibration. After the
replacement assembly is installed, don't forget
to
re-
move the strip of tape that was placed on the link
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