Electrical Maintenance
82
direction with the engine running in high
speed. If it does not run, go to the next step. If
it runs backwards, go to “If Fan Runs
Backwards” on page 82.
3. Check for AC voltage between the T1, T2,
and T3 terminals on the fan harness side of the
contactor for the fan being tested.
Approximately 345 Vac should be present
between each pair. If the voltage is acceptable,
go to step 5. If not, go to the next step.
4. Check for AC voltage between the L1, L2,
and L3 terminals on the generator harness side
of the contactor for the fan being tested.
Approximately 345 Vac should be present
between each pair. If the voltage is acceptable,
go to the next step. If not, go to step 8.
5. Turn the unit off and check the connections in
the junction box for the fan being tested to
make sure they are clean and tight.
6. Check the resistance on the three pairs of
wires (T1-T2, T2-T3, and T1-T3) at the fan
side of the contactor for fan being tested. The
resistance should be approximately 7.7 ohms
on each pair. If not, go to the next step.
7. Check the continuity of the T1, T2, and T3
wires from the contactor for fan being tested
to the fan. If all three wires have good
continuity, the fan motor is probably faulty.
8. Turn the unit off and check the T1/L1, T2/L2,
and T3/L3 circuits (including any contactors)
back to the AC generator for continuity. If the
T1/L1, T2/L2, and T3/L3 circuits all have
good continuity, test the AC generator.
If Fan Runs Backwards
Make sure the unit is turned off. Check the unit
wiring to make sure it is correct per the schematic
and wiring diagrams on pages 171-183. If all of
the wiring is correct but the fan still runs
backwards, switch the T1 and T2 wire
connections on the fan harness side of the
contactor for the fan being tested. If the fan now
runs correctly, it is probably wired incorrectly.
Evaporator Fans
The evaporator fans are axial blower type fans
mounted on both ends of a single evaporator fan
motor. The evaporator fans (and motor) are
mounted in the evaporator, but are accessed from
the front of the unit through an access panel
located in the top of the unit between the
condenser coils. The evaporator fans rotate up
(from bottom to top) when viewed from the front
of the unit through the access panel.
Because the evaporator fan speed varies with the
engine speed, a two-speed motor and two
contactors are used. When the engine is running in
low speed, the evaporator fan contactor connected
to the high speed windings is energized and the
evaporator fans run at approximately 1770 rpm.
When the engine is running in high speed, the
evaporator fan contactor connected to the low
speed windings is energized and the evaporator
fans run at approximately 1800 rpm. This keeps
the evaporator air flow consistent regardless of the
engine speed.
Test the evaporator fans as follows:
1. Use the Service Test Mode to run the unit in
high speed cool. Refer to the appropriate
Diagnostic Manual for specific information
about the Service Test Mode. The evaporator
fans should run at approximately 1800 rpm in
the correct direction with the engine running
in high speed.If it does not run, go to step 3. If
it runs backwards, go to “If Fan Runs
Backwards” on page 82.
1.
Ground Fault Relay
2.
EFHC—Evaporator Fan High Contactor
3.
EFLC—Evaporator Fan Low Contactor
4.
CCFC—Condenser Fan Curbside Contactor
5.
CRFC—Condenser Fan Roadside Contactor
Figure 152: Fan Control Box with Cover Removed
ARA1907
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