Carrier 68RM35-610 Operation And Service page 42

4.12.2 Superheat Measurement
NOTE
All readings must be taken from the TXV bulb
location and out of the direct air stream.
3
2
1
1. Suction Line
(section view)
2. TXV Bulb Clamp
3. Nut & Bolt (clamp)
Figure 4-10.Thermostatic Expansion Valve Bulb
and Thermocouple
a. Remove Presstite insulation from expansion valve
bulb and suction line.
b. Loosen one TXV bulb clamp and make sure area un-
der clamp is clean.
c. Place temperature thermocouple in contact with the
suction tube and parallel to the TXV bulb, and then
secure loosened clamp making sure both bulb and
thermocouple are firmly secured to suction line.
(SeeFigure 4-10.) Reinstall insulation around the
bulb.
d. Connect an accurate low pressure gauge to the low
pressure port (Figure 1-9, 22).
e. Start bus and run on fast idle until unit has stabilized,
about 20 to 30 minutes.
NOTE
When conducting this test, the suction pressure
must be at least 6 psig (0.41 bar) below the ex-
pansion valve maximum operating pressure
(MOP). Refer to paragraph 1.7 for MOP.
f. Using the temperature/pressure chart (Table 4-4),
determine the saturation temperature corresponding
to the evaporator outlet pressure.
g. Note the temperature of the suction gas at the expan-
sion valve bulb. Subtract the saturation temperature
from this temperature. The difference is the super-
heat of the suction gas.
h. The superheat may cycle from a low to high reading.
Monitor the superheat taking readings every 3--5 min-
utes for a total of 5--6 readings. Calculate the super-
heats, add the readings and divide by the number of
readings taken to determine average superheat. Re-
fer to paragraph 1.7 for superheat setting.
i. If superheat is not within tolerance, replace the valve.
03/11
4
5
4. Thermocouple
5. TXV Bulb (Shown
in the 4'clock
position)
4.13 REPLACING RETURN AIR FILTERS
The return air filters are located behind the return air
grill, inside the vehicle.
The filters should be checked for cleanliness
periodically depending on operating conditions. A dirty
filter will restrict air flow over the evaporator coil which
may cause insufficient cooling or heating and possible
frost buildup on the coil. To remove the filters, do the
following.
a. Place main battery disconnect switch in OFF position
and lock.
b. Remove the return air grille.
c. Loosen filter retaining hardware and remove the filter
from the grille.
d. Reverse procedure to install new filters.
4.14 COMPRESSOR MAINTENANCE
4.14.1 Shaft Seal Reservoir
If compressor is fitted with a shaft seal reservoir, it is
recommended that the reservoir is serviced (checked
and drained) at least once a year. Refer to the 05G Twin
Port Workshop Manual 62--11052 for complete
instructions.
4.14.2 Removing the Compressor
If compressor is inoperative and the unit still has
refrigerant pressure, isolate the compressor and
remove the refrigerant. Refer to paragraph 4.4.2. If
compressor is operative, perform a pump down. Refer
to paragraph 4.4.3.
a. Place main battery disconnect switch in OFF position
and lock.
b. Tag and disconnect wiring to the high pressure and
low pressure switch, unloaders and clutch.
c. Remove tension on drive belts, remove drive belts.
d. Loosen bolts at suction and discharge service valve
flanges and break seal to be sure pressure is re-
leased. Remove bolts.
e. Remove four bolts holding compressor to base
f. Attach sling or other device to the compressor and re-
move compressor from the coach through the access
door.
1. Service replacement compressors are sold
without service valves. Valve pads are
installed in their place. The optional
unloaders are not supplied, as the cylinder
heads are shipped with plugs. The
customer
unloader valves for use on the replacement
compressor.
2. The piston plug that is removed from the
replacement compressor head must be
installed in the failed compressor if
returning for warranty or core credit.
3 Do not interchange allen--head capscrews
that mount the piston plug and unloader,
they are not interchangeable.
4--9
NOTES
should retain the original
T356