MCi Crusader II 1989 Maintenance Manual page 484

Date
1-1-89
Page
16-14
MC-9 MAINTENANCE MANUAL
FANS AND MOTOR
Evaporator blowers are mounted on the shafts of a 1
½
hp
(1.1 kw} 24-volt motor. They should be cleaned periodically,
the frequency depending on operating conditions. A dusty
environment will mean more frequent cleaning. Use com-
pressed air to clean the fans.
The motor (single speed) should be checked every 5,000
operating hours (more often in dusty environments). Lubri-
cation is not necessary since the motor is a sealed, self-
lubricated unit. However. the brushes should not be allowed
to wear shorter than¾" (19 mm).
To test the current draw of the motor, proceed as follows:
1. Connect an ammeter in series with the motor lead. The
ammeter hook-up mustallowtheevaporatordoorto be fully .
closed during the check.
2. Start the engine and set at fast idle.
3. Place the A/C-Heat Switch in the A/C position.
4. Observe the ammeter reading. Current draw should be
48-52 amps at 27.2
voe.
5. Check and replace the motor brushes if motor draws
excessive current. Minimum brush length is¾" (19 mm}.
CAUTION: Do not use emery cloth or
sandpaper for seating brushes or cleaning
commutators. Seat new brushes with a
bedding stone.
6. If the brushes are satisfactory, replace the motor.
FILTER
NOTE: Fans and tapered lock bushings
are dynamically balanced. Before remov•
ing the bushing, match•mark the fan and
bushing to allow re-installation in the
same position.
At intervals depending on service conditions, the A/C air
filter should be removed and the following procedure fol-
lowed for cleaning:
1 . Shake out excessive dirt and grit.
2. Wash in warm water and if excessively dirty, use a mild
laundry detergent in warm water.
3. Rinse thoroughly and shake out excess water.
4. Let dry and replace in service.
To reach the filter, open the battery compartment door,
unlatch locks and pull out filter. The filter is provided with a
grab handle for removal. See figure 16-1.
CAUTION: The coach should never be
operated without this filter because proper
circulation would be impaired. All air
would bypass from pressure to the_ suc-
tion side of the chamber.
RECEIVER TANK
The receiver tank is located in the condenser compart-
ment. The sight glasses can be observed by opening the
condenser compartment door (figure 16-14).
The function of the receiver tank is to store the liquid
refrigerant. Du ring normal operation, the level of the refrig-
erant should be approximately at the halfway mark on the
lower glass.
JL
•
---
t
.J
FREON LEVEL - ,
INDICATOR \
•
[.
,~~ · ~
. .
Figure 16-14: Receiver Tank
In case of extreme pressure rise in the liquid receiver
tank. a pressure relief valve will break at 385 psi:!: 10 psi.
(:;!,655 kPa.:!69 kPa), and relieve the receiver tank pressure.
The receiver tank incorporates an inlet-valve at the inlet
. side which allows the tank to be isolated for service. An
outlet valve at the outlet side permits complete isolation
from the rest of the system.
PURGING SYSTEM AT RECEIVER TANK
Abnormal high head pressure sometimes indicates non-
condensible gases in the receiver tank. In order to purge
suc.h gases that might accumulate in the system, use the
test gauge fitting on the intake valve to purge the receiver
tank. ·
The system requires 24 lbs. (10.8 kg) of Freon 12. The
liquid should be approximately½ in lower sight glass after
30 minutes of engine op·eration in fast idle with coach inter-
ior at approximately 70°F. (21 °C.}.
Refrigerant liquid should never be visible in upper sight
glass and refrigerant should not be added unless the system
has been operated as previously outlined.
FIL TEA-DRYER
A filter-dryer (figure 16-15) is installed between the
receiver tank and expansion valve. It is used to absorb
moisture from the refrigerant.
A plugged filter-dryer is indicated by differences in
temperature on either side of it. If plugged, the filter-dryer
must be replaced by following this procedure:
1. Pump down the system by isolating the refrigerant in
the receiver and reducing pressure at the dryer.
2. Install a service gauge at the compressor.
3. Close off the outlet from the receiver tank.
4. Run the compressor until the low side of the system is
evacuated.
5. Change the filter-dryer element.