Honeywell thermostat error code e1, 53, 89, 90

Honeywell thermostat error code e1


If you see E1 or E, please, check the code number on the right side of the display:

23 – EIM lacks dual fuel capability. If you have fossil fuel backup heat, replace EIM. If you have electric backup heat, check and select Installer Setup Function 4 to ELECTRIC.

29 – The device is trying to connect incompatible wireless units.

30 – Invalid zone number. Set it to zero.

33 – Check Return Air Sensor wiring. If you have to remove the sensor, press and hold the CONNECT button on the EIM for 10 seconds until it starts flashing orange.

34 – Low signal. Take wireless device to a different place and try again.

38 – Make sure the “Connected” indication on EIM is flashing and you are at least feet away from EIM.

53 – The unit is not getting Outdoor Temperature and Outdoor Humidity:

  1. Check the thermostat’s configuration. It may be set for compressor lockout, dual fuel, or auxiliary lockout with no outdoor sensor. Connect the outdoor sensor to the EIM using the Wireless Setup function.
  2. If E53 is still there, outdoor sensor is not connecting properly. Insert two fresh AA Lithium batteries in it.


Honeywell thermostat error code 53

This code indicates failing outdoor sensor. Check the sensor and wiring. If there are no visible faults, replace the sensor.


Honeywell thermostat error code 89

The 89 error code stands for “Cooling/heating unit missing”. Most likely, there is a connection problem in the wiring harness. This happens due to wires breaking, connections getting loose or units failing. Finally, a fuse in the Outside compressor unit may need to be replaced.


Honeywell thermostat error code 90

The 90 error code occurs when there is an issue in the thermostat module, poor connection in the air handler unit or when the circuit board goes faulty (the one where the thermostat wire connections are located).


No power to Honeywell thermostat? Here’s a fix