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Error code · Room Air Conditioner

GE Zoneline AZ90 Code 4: Indoor coil sensor on a default value

On the earlier GE Zoneline AZ90 and AZ91 single-package vertical units, including the AZ90E09D2C, code 4 tells you the indoor coil temperature sensor is open or shorted. The control defaults to a value of 40°F and…

Low risk · DIY check OK
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Code
4
Appliance
Room Air Conditioner
Brand
GE
Warranty
30-day workmanship

What 4 means

On the earlier GE Zoneline AZ90 and AZ91 single-package vertical units, including the AZ90E09D2C, code 4 tells you the indoor coil temperature sensor is open or shorted. The control defaults to a value of 40°F and keeps operating. That sensor helps guard against coil icing, so protection against freezing is less precise while the code is active. On the newer AZ95 generation, code 4 refers to an indoor thermistor.

Common causes of 4

  • Indoor coil sensor open or shorted
  • Sensor connection at the control
  • Sensor reading out of range
✓ One safe check you can try

1. Tap ENTER to read what the control has stored; SCROLL goes to the next entry. 2. Make sure the filter and front grille are clean so airflow stays strong. 3. Run the unit normally and watch for ice or poor cooling. 4. Report poor cooling or frost to your property manager. 5. After service, hold ENTER and SCROLL together for 3 to 6 seconds to clear the history.

! Why to stop there
  • Because the control keeps going on a default value, the sensor problem can go unnoticed for a while.
  • We test the coil sensor and watch the coil behavior.
  • You see a written price before work starts, and our repair has a 30-day workmanship warranty.
Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.
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Other Room Air Conditioner codes

Temperature display flashingGE Zoneline AZ41 AZ61 Temperature Display Flashing: Unit Alert 31GE Zoneline AZ95 Code 31: Lost contact with the 2-way thermostat 22GE Zoneline AZ90 Code 22: Outdoor Coil Frost Protection 32GE Zoneline AZ95 Code 32: Thermostat sensor data being ignored FRZGE Zoneline AZ90 Code FRZ: Room Freeze Protection 1GE Zoneline AZ90 Code 1: Button stuck down over 20 seconds E1GE Portable AC Code E1: Room Temperature Sensor 2GE Zoneline AZ90 Code 2: Supply voltage outside the allowed range
44 questions
Is the unit safe to run with code 4?

It keeps operating on a default value, so yes for short term. Poor airflow could allow the coil to ice more easily, so keep filters and grilles clear.

What is the 40°F default for?

It gives the control a safe working value when the real coil reading is lost, so it can carry on without shutting down. The default keeps the unit operating through the problem.

Is this the same as AZ95 code 4?

No. The AZ95 code 4 is an indoor thermistor error that removes cooling. The AZ90 and AZ91 version keeps running. Check your label to see which generation is installed.

Book a visit

Still unsure about 4?

A technician diagnoses it on site and gives you the price in writing before any work starts.

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