86
TK 56433-5-MM-EN
Figure 110.
Evaporator Blower Housing
1.
Damper Stop
3.
Damper Gear Motor
2.
Damper Door (Open)
4.
Scroll Panel
The unit is equipped with a base controller that
contains a a damper gear motor drive to control the
damper gear motor. The base controller used in trailer
units without the damper gear motor will not work with
the damper gear motor. Make sure to order the correct
base controller if it is being replaced.
The defrost damper is open when the unit is in Cool or
Heat, and closes when the unit is in Defrost. To close,
the damper gear motor moves the damper door down
until it contacts the top of the scroll panel. To open, the
damper gear motor moves the damper door up until it
contacts the damper stops.
Alarm Code 29 – Check Defrost Damper Circuit and
Alarm Code 30 – Defrost Damper Stuck are associated
with the defrost damper.
•
Alarm Code 29 is set during the Pretrip Test if the
controller senses a fault in the damper gear motor
operation.
•
Alarm Code 30 is set any time the controller tries to
move the damper and the damper gear motor
draws excessive current for a specified time.
In some conditions, such as when the unit is turned off,
the damper is left in the last position to minimize
operation and wear on the damper gear motor.
Testing Defrost Damper
The damper operation can be tested as part of the
Pretrip Test, or by using the Interface Board Test Mode.
P
Prre
ettrriip
p T
Te
esstt
•
Closes then opens the damper
•
Checks amp draw while damper moving
•
Alarm Code 29 is recorded if the damper fails the
test.
IIn
ntte
errffa
acce
e B
Bo
oa
arrd
d T
Te
esstt M
Mo
od
de
e
•
This test is used to verify the damper will move.
•
LED 31 Damper Door Open and LED 32 Damper
Door Close illuminate as required.
•
The initial (breakaway) current draw occurs over a
very short period of time and cannot be accurately
measured. Once the motor is running, the current
draw should not exceed 0.8 amps.
•
A technician must visually verify the damper will
move.
Troubleshooting Defrost Damper
A problem with a damper will usually generate Alarm
Code 29 or Alarm Code 30.
A
Alla
arrm
m C
Co
od
de
e 2
29
9 –– C
Ch
he
ecckk D
De
effrro
osstt D
Da
am
mp
pe
err C
Ciirrccu
uiitt
Alarm Code 29 indicates that the amp draw on the
damper gear motor circuit was out of the expected
range.
1. Visually check the damper door to see that is not
damaged and is attached to the damper gear motor
shaft.
2. Use the Interface Board Mode to see if the damper
moves. Verify LED 31 Damper Door Open and LED
32 Damper Door Close illuminate as required.
3. Check the continuity of the GMRED and GMBLK
circuits from the J15 connector on the base
controller to damper gear motor.
4. Disconnect the damper gear motor harness from
the main harness at the J16 connector near the
damper motor. Check the resistance of the damper
gear motor between pins 1 and 2 in connector on
the damper gear motor harness. The resistance
should be 4 to 5 ohms. If the resistance is out of this
range, check the continuity of the wires from the
connector to the damper gear motor. If these wires
have good continuity, the damper gear motor is
probably defective.
A
Alla
arrm
m C
Co
od
de
e 3
30
0 –– D
De
effrro
osstt D
Da
am
mp
pe
err S
Sttu
ucckk
1. Visually check the damper door to see that is not
damaged, stuck, or frozen in place.
2. Use the Interface Board Mode to see if the damper
moves. Verify LED 31 Damper Door Open and LED
32 Damper Door Close illuminate as required.
3. Check the continuity of the GMRED and GMBLK
circuits for a short to ground.
4. Disconnect the damper gear motor harness from
the main harness at the J16 connector near the
damper motor. Check the resistance of the damper
gear motor between pins 1 and 2 in connector on
the damper gear motor harness. The resistance
should be 4 to 5 ohms. If the resistance is out of this
range, check the continuity of the wires from the
