4
If the circuit is competed to a particular component
and that component will not operate, the problem is
in the roof top unit.
b. Roof Top Heat Pump
The operation of the AC control box can be checked
at the 6-pin plug connection. See FIG. 6. When the
Comfort Control Center is set to operate the heat
pump the fan will operate in the low speed only in the
Auto fan mode.Disconnect the unit and use a 115 volt
light bulb to checkfrom terminal 5 (the white or com-
mon wire) to:
Terminal 1 (blue) is the compressor
Terminal 2 (black) is high speed fan
Terminal 3 (yellow) reversing valve - this wire is ener-
gized in cooling mode only
Terminal 4 (red) is low speed fan
Terminal 6 (green/yellow) chassis ground
If the circuit is completed the light bulb will illumi
nate.
Note: Do not use a voltmeter to do the above tests
as it will give erroneous readings.
If the circuit is completed to a particular component
and that component will not operate, the problem is
in the roof top unit. NEVER MIX 4 button circuit
boards and Comfort Control Centers with the 5
button circuit boards and Comfort Control Cen-
ter.
c. Single Basement Air Conditioners and Heat
Pumps
The single air conditioner/heat pump require check
out and replacement of the AC power module board
only. The diagnosis of the board would be similar to
the complete control box except the tests are done
directly on the board. See FIG. 7.
The proper location of the remote sensor is very important
to maintain a comfortable temperature in the RV. The fol-
lowing rules should be observed when selecting a location:
a. Locate the remote sensor 54" above the floor.
b. Install the remote sensor on a partition, never on an
outside wall.
c. Avoid locations that are close to doors that lead out-
side, windows or outside adjoining walls.
d. Keep them away from discharge from supply registers.
e. Place them in areas that have good air movement.
Avoid corners and under cupboards.
Unplug the remote sensor and test its cable with an ohm-
meter. See figure 10. The ohm reading should be as follows:
TEMPERATURE OHM READING
55
o
F 11667
60
o
F 10212
65
o
F 8959
70
o
F 7876
75
o
F 6939
80
o
F 6126
85
o
F 5418
90
o
F 4802
95
o
F 4264
100
o
F 3793
Note: Any ohm reading has a tolerance of plus or minus
10%.
7. WIRING
Mis-wiring or loose wires can cause electrical short or com-
ponent failure. Use the wiring diagram to verify and correct
wiring. Loose terminals should be tightened or replaced.
8. AC POWER MODULE
The AC power module board consists of a relay, dip switches,
plug receptacles and other electrical components. If an one
of these are defective the complete AC Control Box (some
models only AC power module) must be replaced. The 3
amp fuse is the only replaceable part on the module board.
The board receives messages from the Comfort Control
Center, and completes AC circuits to operate the unit. Be-
fore diagnosing the AC power module, make sure the con-
figuration, DC and AC voltages and operation is correct.
a. Roof Top Air Conditioners
The operation of the AC control box can be checked
at the 6-pin plug connection. Disconnect the unit
and use a 115 volt light bulb to check from terminal 5
(the white or common wire) to:
Terminal 1 (blue) is the compressor
Terminal 2 (black) is high speed fan
Terminal 3 (yellow) is medium speed fan
Terminal 4 (red) is low speed fan
Terminal 6 (green/yellow) chassis ground
If the circuit is completed the light bulb will illuminate.
Note: Do not use a voltmeter to do the above tests as it will
give erroneous readings.
FIG. 7
FIG. 6
WHITE
COMMON
Manual Compliments of
Northwest RV Supply
Printed From
http://www.nwrvsupply.com
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