Blower on after power-up. The service label calls this normal operation. The blower runs for 90 seconds if the furnace was powered up during a call for heat, or if that call opened during the blower on-delay.
Likely causes
- 115 VAC or 24 VAC power came up while a call for heat was present (R-W closed)
- The heat call opened during the blower on-delay
How to fix 12: safe DIY steps
- Count 1 short flash and 2 long flashes. If the blower stops after about 90 seconds, that matches the label
- If the blower never stops, the call for heat may still be closed. A technician checks that circuit. Code 12 is not a limit lockout and not an ignition lockout
Capacitors can hold a charge after the power is off. Safety terms.
When to call a pro
Call a licensed HVAC technician if the blower runs and the burners never light, or if the blower does not stop. A 90-second run right after power returns is the normal code 12 the label describes.
Find a Carrier dealer (official locator, opens in a new tab) ↗Email me this fix
We save your email and this page. Nothing is emailed. We'll only use your email for this request.
Request a filter and maintenance reminder
We save your email, this page, and the interval you pick. Nothing is emailed. We'll only use your email for this request.
Parts & tools for this fix
Taken from this code's causes or steps. A search link opens Amazon results and does not confirm a fit. Check the model number in the manual.
Furnace blower (circulator) motor: guide
In this code: The heat call opened during the blower on-delay
This one is for a technician to test or replace, so we only explain it and do not link to buy it.
High limit and rollout switches: guide
In this code: If the blower never stops, the call for heat may still be closed. A technician checks that circuit. Code 12 is not a limit lockout and not an ignition lockout
A safety device: we explain it but do not link to buy one.