56 Air and coil sensors disagree

What the control is telling you

The air and coil thermistor readings do not make sense together. Cooling: air sensor more than 10°F warmer or 20°F cooler than the coil sensor. Heat pump heating: more than 35°F warmer or 10°F cooler.

Applies to: KeepRite *SA5/*SA6 AC and *SH4/*SH5/*SH6 HP single-stage communicating; *CA7/*CA9 AC and *CH6/*CH9 HP two-stage communicating

Likely causes

• One sensor drifting or misplaced
• Sensor relocated from its factory spot
• Wiring fault

Test and repair steps

1. Ohm both sensors and compare with the chart.
2. Check both are in their factory locations (do not move them).
3. Check wiring; replace the faulty sensor.

Models that show this code

11 models in KeepRite *SA/*SH Single-Stage Communicating, KeepRite *CA/*CH Two-Stage Communicating

Other codes on the same units

• 46 Brown-out (low voltage)
• 47 No 230 V at the unit
• 53 Outdoor air temperature sensor fault
• 55 Outdoor coil sensor fault
• 71 Low stage thermal cutout
• 72 Compressor thermal cutout (two-stage: high stage)
• 73 Contactor stuck closed
• 74 No 230 V at compressor