To Check/Measure Superheat; Model 05G Compressor Maintenance; Removing The Compressor; Thermostatic Expansion Valve Bulb And Thermocouple Installation - Carrier 68G5-105 Series Operation & Service Manual

c. Loosen retaining straps holding bulb to suction line
and detach bulb from the suction line.
d. Loosen flare nut on equalizer line and disconnect
equalizer line from the expansion valve.
e. Remove capscrews and lift off power head and cage
assemblies and gaskets.
f. Check, clean and remove any foreign material from
the valve body, valve seat and mating surfaces.
NOTE
Do not adjust the new replacement expansion
valve. Valves are preset at the factory.
g. Using new gaskets, install new cage and power head
assemblies provided with repair kit.
h. The thermal bulb is installed below the center of the
suction line (four or eight o'clock position). This area
must be clean to ensure positive bulb contact. Strap
thermal bulb to suction line and insulate both with
"Presstite." Ensure that retaining straps are tight.
(See Figure 4-7)
i. Connect equalizer line to the expansion valve.
j. Evacuate and dehydrate. (Refer to paragraph 4.6)
k. Open filter-drier inlet valve (liquid line service valve)
and all service valves.
l. Run the coach for approximately 30 minutes on fast
idle.
m.Check refrigerant charge. (Refer to paragraph 4.7.1)
n. Check superheat. (Refer to paragraph 4.11.2)
3
2
1
1. Suction Line (end view)
2. TXV Bulb Clamp
3. Nut and Bolt (clamp)
4. Thermocouple
5. TXV Bulb (Shown in the
four o'clock position)
Figure 4-7. Thermostatic Expansion Valve
Bulb and Thermocouple Installation

4.11.2 To Check/Measure Superheat

NOTE
All readings must be taken from the leaving side
of the evaporator.
a. Open filter access door.
b. Remove Presstite insulation from expansion valve
bulb and suction line.
c. Loosen one TXV bulb clamp and make sure area
under clamp (above TXV bulb) is clean.
T-312
d. Place temperature thermocouple in contact with the
suction tube and parallel to the TXV bulb, and then
secure loosened clamp making sure both bulbs are
firmly secured to suction line. (See Figure 4-7)
Reinstall insulation around the bulb.
e. Connect an accurate low pressure gauge (or install a
manifold gauge set) to the service port on the leaving
side of the evaporator. (Refer to paragraph 4.3)
f. Close evaporator access door being careful to route
thermocouple sensing wire and guage hose thru the
access hole to outside the evaporator.
g. Start coach and run on fast idle until unit has
stabilized, about 20 to 30 minutes.
h. From the temperature/pressure chart, determine the
saturation
evaporator outlet pressure. (Refer to Table 4-6)
i. Note the temperature of the suction gas at the
expansion valve bulb. Subtract the saturation
temperature determined in step 8 from the
temperature measured in this step. The difference is
the superheat of the suction gas.
j. Repeat steps 8. and 9. six times at three minute
intervals and average the six readings to determine
average superheat. Average superheat should be 12
to 18_F (6.7 to 10.1_C).

4.12 MODEL 05G COMPRESSOR MAINTENANCE

4.12.1 Removing the Compressor

If compressor is inoperative and the unit still has
refrigerant pressure, isolate the compressor and
4
remove the refrigerant. (Refer to paragraph 4.4.3)
5
If compressor is operative, perform a pump down.
(Refer to paragraph 4.4.4)
a. Turn main battery disconnect switch to OFF position
and lock.
b. Loosen the compressor drive belt, and remove.
c. Loosen bolts at suction and discharge service valve
flanges and break seal to be sure pressure is
released.
d. Remove bolts from suction and discharge service
valve flanges.
e. Tag and disconnect wiring to the high pressure cutout
switch, discharge pressure transducer, suction
pressure transducer, unloaders and the clutch.
f. Remove four bolts holding compressor to base.
g. Attach sling or other device to the compressor and
remove compressor from the coach through the right
rear access door.
h. Set the compressor on a sturdy work surface.
4-8
temperature corresponding to the