What causes Carrier Gas Furnace CL?

Nothing is wrong: the thermostat is calling for cooling or heat pump heat, which is exactly when CL is supposed to show. The blower is finishing its cool-off delay (5, 30 or 90 seconds) after the thermostat was satisfied. Someone scrolled into the Main Menu, where CL is the cooling and heat pump blower-speed setting rather than a status. If CL shows but the house isn't cooling, the furnace is getting the call and running the blower; the problem is usually the outdoor unit, its power, or airflow. A dirty air filter or blocked return grilles, which cut airflow and cooling even when the display looks normal. A thermostat in Cool or heat pump mode when you expected gas heat, so the furnace shows CL instead of Ht.

How do I fix Carrier Gas Furnace CL?

Read what the display shows once it returns to status. CL, iDL, Ht, HPd, CFn and bLr are normal operating modes. A number with a decimal, like 33.1 or 13.1, is an active fault; look up that code instead. If the house is cooling, leave it alone. CL will change to iDL after the thermostat is satisfied and the cool-off delay ends. If the blower runs but the air isn't cold, go outside and check whether the outdoor unit's fan and compressor are running. If not, check its breaker in the main panel and the disconnect box next to the unit. Replace the furnace air filter and make sure supply and return vents aren't blocked or closed. Check the thermostat is set to Cool with a setpoint below room temperature (or to Heat if you wanted gas heat), and replace its batteries if it uses them. If you landed in the menu by pressing buttons, wait 60 seconds without touching anything and the display goes back to status. Don't change the CL blower-speed setting: Carrier says it must match the airflow your outdoor equipment requires.

When should I call a pro for Carrier Gas Furnace CL?

The display shows CL and the blower runs, but the outdoor unit won't start even with its breaker and disconnect on. That points to parts like a capacitor or contactor, which are high-voltage work. The outdoor unit runs but the air isn't cool, or you see ice on the refrigerant lines or indoor coil. That can mean low refrigerant or a coil problem, which needs a licensed technician. The display shows a ##.# fault code, or the status LED is flashing a code, and it keeps coming back. The cooling airflow (CL blower speed) needs setting to match a new air conditioner or heat pump. Carrier points installers to the outdoor equipment data and the furnace's air delivery table for that. Working with the blower door off. The door switch cuts 115-volt power to the control, and Carrier warns not to tape or bypass it.

Code: CL🔥 Carrier Gas Furnace

Carrier Furnace Code CL: Cooling Mode, Not an Error (Meaning and What to Check)

Q: What does Carrier Gas Furnace CL mean?

CL on a Carrier furnace's 3-digit display means Cooling Mode: the thermostat is calling for cooling or heat pump operation and the furnace blower is moving the air. It's a status readout, not a fault. Real Carrier faults on these displays show as a number with a decimal, such as 33.1, where the first two digits are the major code and the third is the minor code. Newer Carrier gas furnaces with an on-board 3-digit LCD display, such as the 59SC6A condensing furnace and the 58SC0B 80% furnace, show the system's status after startup or after no buttons have been pressed for 60 seconds. Carrier's System Status Display Codes table lists CL as Cooling Mode, meaning cooling or heat pump is active. The other status displays are iDL (idle, no demand), Ht (gas heating), HPd (gas heat during a heat pump defrost), CFn (continuous fan) and bLr (the secondary furnace of a twinned pair running its blower). In cooling, the thermostat closes R to Y, which starts the outdoor unit and runs the furnace blower on its COOL speed. When the thermostat is satisfied, the outdoor unit stops and the blower keeps running at cool speed for a cool-off delay of 5, 30 or 90 seconds (90 from the factory), so CL can stay on briefly after the outdoor unit shuts off. CL also appears in the furnace's Main Menu, where it is the Cooling and Heat Pump blower speed setting rather than a status. A fault shows as ##.#, and the status LED also flashes the major code (short flashes for the first digit, long flashes for the second).

Reviewed 2026-10-22 · Based on 3 manufacturer & service sources

What the code means

Newer Carrier gas furnaces with an on-board 3-digit LCD display, such as the 59SC6A condensing furnace and the 58SC0B 80% furnace, show the system's status after startup or after no buttons have been pressed for 60 seconds. Carrier's System Status Display Codes table lists CL as Cooling Mode, meaning cooling or heat pump is active. The other status displays are iDL (idle, no demand), Ht (gas heating), HPd (gas heat during a heat pump defrost), CFn (continuous fan) and bLr (the secondary furnace of a twinned pair running its blower). In cooling, the thermostat closes R to Y, which starts the outdoor unit and runs the furnace blower on its COOL speed. When the thermostat is satisfied, the outdoor unit stops and the blower keeps running at cool speed for a cool-off delay of 5, 30 or 90 seconds (90 from the factory), so CL can stay on briefly after the outdoor unit shuts off. CL also appears in the furnace's Main Menu, where it is the Cooling and Heat Pump blower speed setting rather than a status. A fault shows as ##.#, and the status LED also flashes the major code (short flashes for the first digit, long flashes for the second).

Likely causes

Nothing is wrong: the thermostat is calling for cooling or heat pump heat, which is exactly when CL is supposed to show
The blower is finishing its cool-off delay (5, 30 or 90 seconds) after the thermostat was satisfied
Someone scrolled into the Main Menu, where CL is the cooling and heat pump blower-speed setting rather than a status
If CL shows but the house isn't cooling, the furnace is getting the call and running the blower; the problem is usually the outdoor unit, its power, or airflow
A dirty air filter or blocked return grilles, which cut airflow and cooling even when the display looks normal
A thermostat in Cool or heat pump mode when you expected gas heat, so the furnace shows CL instead of Ht

Safe DIY checks

⚠ Before you start

Turn off power at the furnace/HVAC service switch and the breaker before opening panels. Shut the gas valve before any work near the burners, and never disconnect or alter the gas line. If you smell gas, leave the house and call your gas utility.

Read what the display shows once it returns to status. CL, iDL, Ht, HPd, CFn and bLr are normal operating modes. A number with a decimal, like 33.1 or 13.1, is an active fault; look up that code instead.
If the house is cooling, leave it alone. CL will change to iDL after the thermostat is satisfied and the cool-off delay ends.
If the blower runs but the air isn't cold, go outside and check whether the outdoor unit's fan and compressor are running. If not, check its breaker in the main panel and the disconnect box next to the unit.
Replace the furnace air filter and make sure supply and return vents aren't blocked or closed.
Check the thermostat is set to Cool with a setpoint below room temperature (or to Heat if you wanted gas heat), and replace its batteries if it uses them.
If you landed in the menu by pressing buttons, wait 60 seconds without touching anything and the display goes back to status. Don't change the CL blower-speed setting: Carrier says it must match the airflow your outdoor equipment requires.

🛠 When to call a pro

The display shows CL and the blower runs, but the outdoor unit won't start even with its breaker and disconnect on. That points to parts like a capacitor or contactor, which are high-voltage work.
The outdoor unit runs but the air isn't cool, or you see ice on the refrigerant lines or indoor coil. That can mean low refrigerant or a coil problem, which needs a licensed technician.
The display shows a ##.# fault code, or the status LED is flashing a code, and it keeps coming back.
The cooling airflow (CL blower speed) needs setting to match a new air conditioner or heat pump. Carrier points installers to the outdoor equipment data and the furnace's air delivery table for that.
Working with the blower door off. The door switch cuts 115-volt power to the control, and Carrier warns not to tape or bypass it.

Parts that commonly fix it

Always match the part number to your exact model.

⚙

Furnace air filter (your exact size)

A clogged filter is the most common reason cooling feels weak while the display looks normal.

[affiliate link slot: AFFILIATE_SLOT_AIR_FILTER]

⚙

Thermostat batteries (usually AA or AAA)

Check your thermostat for the battery type.

[affiliate link slot: AFFILIATE_SLOT_THERMOSTAT_BATTERIES]

⚙

Outdoor unit run capacitor (match your condenser's rating)

Only if a technician confirms it failed; match the microfarad and voltage ratings on the old part.

[affiliate link slot: AFFILIATE_SLOT_CAPACITOR]

Sources

Last reviewed 2026-10-22. Always confirm against the manual for your exact model number.