York furnace fault code 4
If a thermostat, or a thermostat’s sensor, malfunctions or becomes disconnected from the heating unit, it may have triggered a York furnace fault code 4.
It is important to ensure that if any of these symptoms are present, there is no issue with the wiring of the unit itself.
The York furnace fault code 4 is a general sensor error. It typically means that the sensor could not measure the temperature within the furnace. This can be caused by a dirty or blocked sensor, or something as simple as too many humidifiers in your home or office, causing air moisture levels to be too high for accurate reading of your home’s temperature.
A furnace fault code 4 means that the furnace is not getting enough air, and that part of the problem could be in the pressure switch.
The tech website, Lifehacker.com has a great article about this issue. They provide some troubleshooting tips to understand what might be going wrong with your furnace and how to resolve it.