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Carrier Code 12 - Blower On After Power Up

Code 12 (1 short + 2 long flashes)

Blower came on after restoring power - normal or thermostat issue.

Brand: Carrier (Also covers Bryant, Payne) | Equipment: Gas Furnace

What This Code Means

Code 12 on Carrier (Bryant, Payne) means the blower started immediately after power was restored. This is usually normal if power was cut during a heat cycle, but can also indicate a stuck thermostat call.

Likely Causes (Ranked)

Most common

Power loss during heat cycle

What: Power was cut while furnace was running; blower resumes after cooldown.

How to check: Normal if recent power outage or reset.

Fix: None needed - clears automatically.

Common

Stuck thermostat call

What: Thermostat continuously calling for heat due to wiring short or stuck contact.

How to check: Disconnect thermostat at furnace; if code clears, thermostat issue.

Fix: Inspect thermostat wiring and contacts.

Diagnostic Steps

Wait 5 minutes - code may auto-clear
Check thermostat for stuck call
Inspect wiring
Call tech if persistent

Frequently Asked Questions

Is Carrier code 12 a problem?

Usually no - it's a startup-related code that clears on its own. Only an issue if persistent.

Same on Bryant?

Yes.

DIY?

Yes - wait and observe is the first step.

Related Carrier Codes

Related Symptoms

Need More Help?

Try our interactive symptom diagnostic tool or browse Carrier parts.

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