12
Easy Fix
Carrier · Central Air Conditioners & Furnaces
Blower On After Power-Up
Quick Answer
Error code 12 on your Carrier Central Air Conditioners & Furnaces means: Blower On After Power-Up. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
Likely Causes
How to Fix It
1
Check if thermostat has an active call for fan operation
2
Disconnect thermostat wiring at furnace and check if blower stops
3
Inspect thermostat wiring for shorts between R and G wires
4
If blower continues without thermostat connected, the control board relay may be stuck
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
Thermostat wire (18/5 or 18/8)
Control board (if relay is stuck)
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