Mitsubishi Electric PURY-RP200 Service Handbook page 172

[ IX Troubleshooting ]
1. Error Code
2503
Drain sensor (Thd) fault
2. Error definition and error detection method
If the open or short circuit of the thermistor has been detected for 30 seconds, this condition is considered to be a preliminary
error, and the unit goes into the 3-minute restart delay mode.
If another episode of the above condition is detected during the preliminary error, this is considered a drain sensor error.(If
the short or open circuit of the thermistor is no longer detected, normal operation will be restored in 3 minutes.)
This error is detected when one of the following conditions are met.
∗During Cool/Dry operation
∗Liquid pipe temperature minus inlet temperature is equal to or smaller than - 10°C [ -18°F] (except during the defrost cycle)
∗When the liquid temperature thermistor or suction temperature thermistor or short or open circuited.
∗Drain pump is in operation.
∗One hour has elapsed since the drain sensor went off.
Short: 90°C [194 °F] or above
Open: - 20°C [-4 °F] or below
3. Cause, check method and remedy
(1) Faulty connector (CN31) insertion.
(2) Broken or semi-broken thermistor wire
(3) Thermistor failure
(4) Indoor unit control board (error detection circuit)
failure
HWE10020
Cause Check method and remedy
1) Check for connector connection failure.
Reinsert the connector, restart the operation, and check for
proper operation.
2) Check for a broken thermistor wire.
3) Check the resistance of the thermistor.
0°C[32 °F]:6.0k
10°C[50 °F]:3.9k
20°C[68°F]:2.6k
30°C[86°F]:1.8k
40°C[104 °F]:1.3k
4) Replace the indoor unit control board if the problem recurs
when the unit is operated with the No.-1 and No.-2 pins on
the drain sensor connector (CN31) being short-circuited.
If the above item checks out OK, there are no problems with
the drain sensor.
Turn off the power and turn it back on.
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