4 blinks
Moderate
Trane · HVAC Systems (AC, Furnaces & Heat Pumps)
Open High Temperature Limit Switch
Quick Answer
Error code 4 blinks on your Trane HVAC Systems (AC, Furnaces & Heat Pumps) means: Open High Temperature 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 immediately
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 rating
4
Inspect the blower motor and capacitor for proper operation
5
Measure static pressure in the duct system (should not exceed 0.5 in WC total)
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Parts You May Need
Air filter
High-limit switch
Blower motor run capacitor
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