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By Ashley Sweren
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Posted 8/1/23

If your Carrier furnace is giving you trouble, fixing the problem may be as simple as updating your thermostat settings. Or you may need a hand from a local HVAC pro. Before you pay a service fee, give these Carrier furnace troubleshooting tips a try.

carrier furnace troubleshooting fix

Carrier furnace is not heating or not blowing hot air

Check the air filter; it may be dirty. It’s time to change your filter if it’s gray with a dusty buildup.

You can purchase a new furnace filter at stores like Walmart or Home Depot for less than $20. Our video shows you how to change your furnace filter on your own.

Carrier furnace is cycling irregularly

Dirty filters are the most common cause of furnace cycling issues. Per the instructions above, replace your furnace filter if it’s dirty.

Next, check your thermostat. Turn it off and restart it. Try changing the batteries if it takes them.

Finally, make sure your windows and doors are properly sealed and not leaking air. The Department of Energy has good information on how to detect air leaks.

Carrier furnace is starting and stopping

Set the thermostat to “heat” and either “on” or “auto.” See if the air filter is clean. You may need to replace it with a fresh one.

If the furnace is still not working correctly, make sure all the vents in your home are open and unobstructed.

Carrier furnace is leaking water

In most cases, furnaces leak water because of a clogged condensation drain. This (and any other furnace water leak causes) is best repaired by a professional.

When you notice water leaking from your furnace, turn off the heat via the thermostat. Then turn off the power switch and electrical breaker connected to the furnace. Water plus electricity is a dangerous combination. If you have a gas furnace, turn off the gas line.

Mop up the excess water to avoid water damage and call a certified HVAC technician for repair.

Carrier furnace troubleshooting codes

Your system may be able to help you diagnose the problem when you’re Carrier furnace troubleshooting. Some standard Carrier furnace error codes follow.

Carrier furnace error codeWhat it means
Blinking yellow 3Stuck in high fire mode
Blinking green 4Stuck in low fire mode
11No faults in recent history
12Blower calibration lockout
13Limit switch lockout
14Ignition lockout
21Invalid model selection
22Setup error
23Invalid blower airflow selection
24Secondary voltage fuse is open
31High-pressure switch fault
32Low-pressure switch fault
33Limit switch fault
34Ignition proving fault
41Blower outside valid speed range
42Inducer outside valid speed range
43Pressure switch calibration fault
44Blower calibration fault

Check the error code so you know what to expect before calling a professional for service.

Carrier furnace troubleshooting: model lookup

For additional Carrier furnace troubleshooting information related to your specific model, check out Carrier’s website or the manual that came with your system.

We’ve provided links to the product documentation for Carrier’s current furnace lineup to get you started.

Carrier furnace troubleshooting documentation


Don’t see your model listed? Look it up here.

When to call an HVAC professional

Call an HVAC technician when you’ve tried the Carrier furnace troubleshooting tips above and still can’t solve the problem.

Or, if you’re uncomfortable performing Carrier furnace troubleshooting, a technician can do it for you.

Click below to connect with a local HVAC pro who can help.

DIY didn’t do it for you?