Mitsubishi Electric LAHN-1 Technical & Service Manual page 3

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.
hoods and damper controls are tested at the factory
Operation testing when the outdoor ambient is BELOW 35°F
ore shipping. To perform an operational test once
1. Turn on power to the outdoor unit.
installation has been completed, follow the steps
2. Make sure the outdoor unit is in cooling mode.
ow.
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
eration testing when the outdoor ambient is
designed.
OVE 50°F
Ambient Temp Hood Angle
1. Turn on power to the outdoor unit.
[ °F ]
2. Make sure the outdoor unit is in cooling mode.
-10
-5
3. Locate the outdoor temperature sensing
0
thermistor at the end of the short conduit
5
coming out the side of the control panel, it can
10
be seen inside the plastic shield.
15
4. Using an aerosol dusting sprayer, invert the
20
can and spray the thermistor with very short
25
bursts of the cold liquid. Caution! Do Not
30
35
overspray the thermistor as it could be
40
damaged. It may take 10 – 20 seconds for
45
the internal thermistor temperature to drop.
The damper will start to move toward the
LAHN Damper Hysteresis Control
closed position after the thermistor drops
below 50°F
OPEN
5. Once the thermistor warms above 50°F, it will
move back to the full open position indicating
50
the low ambient kit is working as designed.
45
40
eration testing when the outdoor ambient is
35
LOW 50°F
30
25
1. Turn on power to the outdoor unit.
2. Make sure the outdoor unit is in cooling mode. 20
3. The damper will move toward the closed
15
position to a predetermined position based on
10
the outdoor ambient temperature, indicating
5
the low ambient kit is working as designed.
0
either of these tests work. Proceed with the
-5
-10
= As Temperature Increases
mponent Troubleshooting
= As Temperature Decreases
If neither of these tests work, proceed with the component
troubleshooting instructions.
ow shows what the blinking light sequence means.
© 2019 Mitsubishi Electric US, Inc.
Blink(s) Thermistor Temperature
1
Output Voltage
[ ° ] v
80 8.78
80 8.78
70 7.9
70 7.9
70 7.9
70 7.9
60 7.04
60 7.04
60 7.04
60 7.04
OPEN 2
OPEN 2
Damper Angle [°]
60 70 80
Above 50F
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.
-15 -10 -5

chart, the thermistor needs to be replaced. If it's
suspected that the thermistor is operating inaccurately,
check the tolerance in the following instructions.
If the light is on constantly, the thermistor is open or shorted and
Disconnect the thermistor from the control board.
needs to be replaced. If the blinking light sequence doesn't fall within
Measure the resistance across the two leads. Measure
the range given in the chart, the thermistor needs to be replaced. If
the temperature of the thermistor. (Accuracy on the
it's suspected that the thermistor is operating inaccurately, check the
tolerance in the following instructions.
temperature reading is important to prevent a good
Disconnect the thermistor from the control board. Measure the
thermistor from being replaced).
Resistance
resistance across the two leads. Measure the temperature of the
Compare the ohm reading with the temperature on the
Ω
thermistor. (Accuracy on the temperature reading is important to
chart below. Based on the thermistor temperature the
117960
prevent a good thermistor from being replaced).
Compare the ohm reading with the temperature on the chart below.
100184
ohm reading should be within 1-2% of the number
Based on the thermistor temperature the ohm reading should be within
85340
shown below. If not, and the thermistor connections
3% of the number shown below. If not, and the thermistor connections
72906
are not corroded, the thermistor should be replaced.
are not corroded, the thermistor should be replaced.
62460
53658
46220
o
Ohms
F
39917
86 8,056
84 8,448
34562
82 8,862
30000
81
9,077
26104
79 9,526
22767
77 10,000
75 10,501
73 11,031
72 11,307
70 11,884
68 12,493
66 13,139
64 13,822
63 14,179
61
14,924
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.
Temperature
Outside Ambient Temperature (°F)
0 5 10 15 20 25 30 35 40
(3 Blinks)
 (2 Blinks)
o o
Ohms
F F
59 15,714 32
57 16,551 30
55 17,438 28
54 27
17,902
52 18,873 26
50 19,903 23
48 20,997 21
46 22,159 19
45 22,767 18
43 24,040 16
41 25,394 14
39 26,835 12
37 28,368 10
36 29,171 9
34 7
30,856
Specifications are subject to change without notice.
Outdoor Thermistor Control board
Ohms DC volts output
o
N/A
Above 52 F
52 18,873
50
19,903
45 50 55
 (1 Blink)
o
Ohms Ohms
F
32,650 5 72,906
34,562 3 77,620
36,601 1 82,676
0
37,671 85,340
38,776 -2 90,962
42,315 -4 96,999
44,875 -6 103,486
47,610 -8 110,460
49,047 -9 114,141
52,069 -11 121,921
55,301 -13 130,295
58,759 -15 139,313
62,460 -17 149,030
64,408 -18 154,169
-20
68,510 165,048
Damper
Angle
o
2.00
0 full open
3
2.00 o
0
o
3.25
15