Rheem RHMV2421MNACJA Service Manual page 67

Troubleshooting 12
Evaporator coil middle
temperature sensor error
Detective actuators:
Indoor unit controller PCB
Evaporator coil (MID) thermistor
Detective details:
Indoor unit thermistor is open or short
is detected always.
Forecast of cause:
1. Connector failure connection
2. Thermistor failure
3. Controller PCB failure
Check Point 1 : Check connection of connector
Check if connector is loose or removed
Check erroneous connection
Check if thermistor cable is open
>> Reset power when reinstalling due to removed connector or incorrect wiring.
OK
Check Point 2 : Remove connector and check thermistor resistance value
Thermistor characteristics (Rough value)
-22°F (-30°C)
Temperature
1131.9 kΩ
Resistance value
Temperature 50°F (10°C)
Resistance value 103.3 kΩ
Temperature
104°F (40°C) 113°F (45°C) 122°F (50°C)
Resistance value 25.6 kΩ
If thermistor is either open or shorted, replace it and reset the power.
OK
Check Point 3 : Check voltage of controller PCB (DC5.0V)
Make sure circuit diagram of indoor unit and check terminal voltage at thermistor (DC5.0V)
1
2
CN6
BLACK
3
1 1
BLACK
4 2
-4°F (-20°C) 14°F (-10°C)
579.6 kΩ 312.3 kΩ
59°F (15°C) 68°F (20°C) 77°F (25°C) 86°F (30°C) 95°F (35°C)
80.3 kΩ
20.8 kΩ
H/E (mid.) temp.
thermistor
BLACK
BLACK
2
If the voltage does not appear, replace controller PCB.
Indicate or Display:
Indoor unit
Operation lamp: 4 times Flash,
Timer lamp
Wired remote control
Error code : [E : 42]
Outdoor unit (RP1736/1748HJVXA)
Mode Error
: Light OFF
23°F (-5°C)
233.2 kΩ
62.9 kΩ 49.7 kΩ
131°F (55°C) 140°F (60°C)
17.1 kΩ 14.1 kΩ
03-17
: 2 times Flash
A B C
2 5 15
: Light ON
32°F (0°C) 41°F (5°C)
176.0 kΩ 134.2 kΩ
39.6 kΩ 31.7 kΩ
145.4°F (63°C)
11.6 kΩ 10.4 kΩ
D E F
n : n times blinking