4 blinks
Easy Fix
York · HVAC Systems (AC, Furnaces, Heat Pumps & Thermostats)
Open Limit Switch
Quick Answer
Error code 4 blinks on your York HVAC Systems (AC, Furnaces, Heat Pumps & Thermostats) means: Open Limit Switch. This is usually fixable — see the step-by-step guide below.
Likely Causes
How to Fix It
1
Check and replace the air filter if dirty
2
Verify all supply and return registers throughout the home are fully open
3
Measure temperature rise across the furnace and compare to the nameplate acceptable range
4
Check the blower motor capacitor and test the blower motor for proper operation
5
Clean the blower wheel if dirty buildup is found
Pro Tip
This is a common issue that most users can resolve without specialized tools. Try the first step before moving on to more complex solutions.
Parts You May Need
Air filter
High-limit switch
Blower motor capacitor
Blower wheel cleaning solution
Related Error Codes