Use the sensor’s exact model and measured temperature when checking resistance.
The AC112-01 product data sheet 33-00668-01 specifies a thermistor rated 10 kΩ at 25°C (77°F). Selected values from its resistance table are:
| Temperature | Resistance |
|---|---|
| 0°C / 32°F | 32,651 Ω |
| 5°C / 41°F | 25,395 Ω |
| 10°C / 50°F | 19,903 Ω |
| 15°C / 59°F | 15,714 Ω |
| 20°C / 68°F | 12,493 Ω |
| 25°C / 77°F | 10,000 Ω |
| 30°C / 86°F | 8,056 Ω |
| 35°C / 95°F | 6,530 Ω |
| 40°C / 104°F | 5,325 Ω |
Resistance decreases as this sensor warms. Have a qualified technician isolate power and disconnect the sensor from the control before measuring it. Compare with the sensor’s actual temperature, not only the thermostat setpoint. Do not use an ohmmeter on an energized circuit.
This curve is for the identified AC112-01 sensor. Other two-wire sensors, including other nominal 10 kΩ products, can have different curves; identify the installed sensor and the thermostat’s selected sensor type.
Source: Resideo AC112-01 product data, table 1.
