3 blinks
Easy Fix
Trane · HVAC Systems (AC, Furnaces & Heat Pumps)
Pressure Switch Stuck Closed
Quick Answer
Error code 3 blinks on your Trane HVAC Systems (AC, Furnaces & Heat Pumps) means: Pressure Switch Stuck Closed. This is usually fixable — see the step-by-step guide below.
Likely Causes
How to Fix It
1
Disconnect the pressure switch hose and check if the switch opens using a multimeter
2
Drain any trapped water from the pressure switch hose
3
Verify the pressure switch part number matches the furnace requirements
4
Replace the pressure switch if the contacts remain closed with no pressure applied
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
Pressure switch
Pressure switch tubing
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