3
© 2019 Mitsubishi Electric US, Inc.
Specifications are subject to change without notice.
2. Make sure the outdoor unit is in cooling mode.
3. Locate the outdoor temperature sensing thermistor at the end of
the short conduit coming out the side of the control panel; it can
be seen inside the plastic shield.
4. Using an aerosol dusting sprayer, invert the can and spray the
thermistor with
very short bursts of the cold liquid.
Caution! Do Not overspray the thermistor as it could be
damaged. It may take 10 – 20 seconds for the internal
thermistor temperature to drop.
The damper will start to move toward the closed position after
the thermistor drops below 35°F.
5. Once the thermistor warms above 40°F, it will move back to the
full open position indicating the low ambient kit is working as
designed.
Operation testing when the outdoor ambient is BELOW 35°F
1. Turn on power to the outdoor unit.
2. Make sure the outdoor unit is in cooling mode.
3. The damper will move toward the closed position to a
predetermined position based on the outdoor ambient
temperature, indicating the low ambient kit is working as
designed.
Ambient Temp Hood Angle Output Voltage Resistance
[ °F ]
[ ° ]
v
Ω
-10
80
8.78
117960
-5
80
8.78
100184
0
70
7.9
85340
5
70
7.9
72906
10
70
7.9
62460
15
70
7.9
53658
20
60
7.04
46220
25
60
7.04
39917
30
60
7.04
34562
35
60
7.04
30000
40
OPEN
2
26104
45
OPEN
2
22767
If neither of these tests work, proceed with the component
troubleshooting instructions.
Component troubleshooting
Thermistor
The thermistor is a 10,000 Ω, NTC Type.
The circuit board has a blinking indicator light built in to reference what
the thermistor is sensing. The chart below shows what the blinking
light sequence means.
(1 Blink)
45 50 55
Outside Ambient Temperature (°F)
15 20 25 30 35 40
-15 -10 -5 0 5
10
(3 Blinks)
(2 Blinks)
If the light is on constantly, the thermistor is open or shorted and
needs to be replaced. If the blinking light sequence doesn’t fall within
the range given in the chart, the thermistor needs to be replaced. If
it’s suspected that the thermistor is operating inaccurately, check the
tolerance in the following instructions.
Disconnect the thermistor from the control board. Measure the
resistance across the two leads. Measure the temperature of the
thermistor. (Accuracy on the temperature reading is important to
prevent a good thermistor from being replaced).
Compare the ohm reading with the temperature on the chart below.
Based on the thermistor temperature the ohm reading should be within
3% of the number shown below. If not, and the thermistor connections
are not corroded, the thermistor should be replaced.
All hoods and damper controls are tested at the factory
before shipping. To perform an operational test once
the installation has been completed, follow the steps
below.
Operation testing when the outdoor ambient is
ABOVE 50°F
1. Turn on power to the outdoor unit.
2. Make sure the outdoor unit is in
cooling
mode.
3. Locate the outdoor temperature sensing
thermistor at the end of the short conduit
coming out the side of the control panel, it can
be seen inside the plastic shield.
4. Using an aerosol dusting sprayer, invert the
can and spray the thermistor with very short
bursts of the cold liquid
. Caution! Do Not
overspray the thermistor as it could be
damaged. It may take 10 – 20 seconds for
the internal thermistor temperature to drop.
The damper will start to move toward the
closed position after the thermistor drops
below 50°F
5. Once the thermistor warms above 50°F, it will
move back to the full open position indicating
the low ambient kit is working as designed.
Operation testing when the outdoor ambient is
BELOW 50°F
1. Turn on power to the outdoor unit.
2. Make sure the outdoor unit is in
cooling
mode.
3. The damper will move toward the closed
position to a predetermined position based on
the outdoor ambient temperature, indicating
the low ambient kit is working as designed.
If neither of these tests work. Proceed with the
component troubleshooting instructions.
Component Troubleshooting
Thermistor
The thermistor is a 10,000
Ω
, NTC Type.
The circuit board has a blinking indicator light built in to
reference what the thermistor is sensing. The chart
below shows what the blinking light sequence means.
1
2
3
Constant ON
Thermistor is open or shorted
Blink(s)
Thermistor Temperature
Above 50F
50F to 20F
Below 20F
If the light is on constantly, the thermistor is open or
shorted and needs to be replaced. If the blinking light
sequence doesn’t fall within the range given in the
chart, the thermistor needs to be replaced. If it’s
suspected that the thermistor is operating inaccurately,
check the tolerance in the following instructions.
Disconnect the thermistor from the control board.
Measure the resistance across the two leads. Measure
the temperature of the thermistor. (Accuracy on the
temperature reading is important to prevent a good
thermistor from being replaced).
Compare the ohm reading with the temperature on the
chart below. Based on the thermistor temperature the
ohm reading should be within 1-2% of the number
shown below. If not, and the thermistor connections
are not corroded, the thermistor should be replaced.
o
F
Ohms
o
F
Ohms
o
F
Ohms
o
F
Ohms
86
8,056
59
15,714
32
32,650
5
72,906
84
8,448
57
16,551
30
34,562
3
77,620
82
8,862
55
17,438
28
36,601
1
82,676
81
9,077
54
17,902
27
37,671
0
85,340
79
9,526
52
18,873
26
38,776
-2
90,962
77
10,000
50
19,903
23
42,315
-4
96,999
75
10,501
48
20,997
21
44,875
-6
103,486
73
11,031
46
22,159
19
47,610
-8
110,460
72
11,307
45
22,767
18
49,047
-9
114,141
70
11,884
43
24,040
16
52,069
-11
121,921
68
12,493
41
25,394
14
55,301
-13
130,295
66
13,139
39
26,835
12
58,759
-15
139,313
64
13,822
37
28,368
10
62,460
-17
149,030
63
14,179
36
29,171
9
64,408
-18
154,169
61
14,924
34
30,856
7
68,510
-20
165,048
Circuit Board
Confirm the thermistor is operating properly before
troubleshooting the circuit board.
Make sure the control board has 24 Volts AC when
measured at the
24 VAC
and the
com
terminals. If not,
find the cause of voltage failure.
The circuit board is designed to convert the thermistor
ohm input to a 2 - 9.16 VDC output to control the
position of the damper actuator. Above 2 VDC output
the actuator will start to move the damper toward the
closed position. At 9.16 VDC, the actuator will have
moved 85 degrees and the damper will be
approximately 95% closed.
The damper should never
be 100% closed.
The chart below includes the various
damper angles based on the different outdoor
temperatures. Measure the DC voltage output on the
circuit board at
com (-)
and the
out (+)
terminals. If the
output doesn’t match the thermistor input ohms as
shown below, replace the circuit board.
Outdoor
Thermistor
Control board
Damper
Temperature
Ohms
DC volts output
Angle
Above 52
o
F
N/A
2.00
0
o
full open
52
18,873
2.00
0
o
50
19,903
3.25
15
o
45
22,767
4.50
30
o
40
26,104
5.80
45
o
35
30,000
7.04
60
o
30
34,562
7.90
70
o
25
39,917
8.75
80
o
20
46,220
9.16
85
o
Below 20
o
F
N/A
9.16
85
o
Transformer
December 2013
© 2013 Mitsubishi Electric US, Inc.
3
LAHN Damper Hysteresis Control
OPEN
60
70
80
50
45
40
35
30
25
20
15
10
5
0
-5
-10
= As Temperature Increases
= As Temperature Decreases
Damper Angle [°]
O
ut
doo
r A
m
bi
ent
Te
m
pe
ra
tur
e [
°F]
