55 Outdoor coil sensor fault

What the control is telling you

The outdoor coil thermistor reads open, shorted or out of range.

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

• Failed OCT thermistor
• Wiring or connector fault
• Sensor loose on the tube

Test and repair steps

1. Measure sensor resistance against the chart.
2. Check wiring and the plug.
3. Make sure the sensor is clamped tight on its tube; replace if out of range.

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

• 45 Outdoor control board failure
• 46 Brown-out (low voltage)
• 47 No 230 V at the unit
• 53 Outdoor air temperature sensor fault
• 56 Air and coil sensors disagree
• 71 Low stage thermal cutout
• 72 Compressor thermal cutout (two-stage: high stage)
• 73 Contactor stuck closed