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Carrier gas furnace code 35: Modulating gas valve not communicating
Gas furnace, Canada and United States
The modulating gas valve failed to communicate with the furnace control or respond to its commands, or power to the valve's electronics was interrupted.
On the status light, this code is 3 short flashes, then 5 long flashes.
This needs a licensed gas technician. There is nothing safe to check yourself. Leave the covers on and book a professional.
This involves the gas supply or burner. Only a licensed technician should open the unit or work on gas parts.
Only some models show this code. Check the list below.
What causes it
-
An intermittent wire or poor connection between the gas valve and the furnace control.
How to read this code on your unit
The amber status light (red on some older boards) on the furnace control shows through a small window in the blower access door. A steady light means the control has power and no fault to show. A code is two digits. Count the short flashes for the first digit, then the long flashes for the second, so 3 short flashes followed by 3 long flashes is code 33, and 1 short then 1 long is code 11. Write the code down before you open the door or switch the furnace off.
Booking a licensed gas technician
Book a licensed gas technicianlicensed gas technician
- Turn the unit off and leave the covers on. Gas components must only be serviced by a licensed technician.
- Note the code, how often it appears, and the model and serial numbers from the rating label.
- Book a licensed gas technician and give them those details.
Models that show this code
12 models in 2 ranges
Where this comes from
- 59MN7A modulating condensing gas furnace, installation, start-up, operating and service instructions (59MN7A-12SI) , page 72, 91
- 59MN7B modulating condensing gas furnace, installation, start-up, operating and service instructions (59MN7B-02SI) , page 73
Checked against the manufacturer's manual on 11 October 2026.
Other Carrier gas furnace codes
| Code | Meaning | What you can do |
|---|---|---|
| 21 | Gas heating lockout, fault in the gas valve circuit | Safe checks first, then a pro |
| 22 | Flame sensed while the gas valve is off | Safe checks first, then a pro |
| 31 | Flue or venting fault (depends on model) | Safe checks first, then a pro |
| 32 | Low or low-heat pressure switch did not close, or opened again | Safe checks first, then a pro |
| 33 | Limit circuit fault, a limit or rollout switch is open | Safe checks first, then a pro |
| 34 | Flame not proved during ignition | Safe checks first, then a pro |
| 41 | Blower motor fault, speed or communication lost | Call a pro |
| 42 | Inducer motor fault | Safe checks first, then a pro |
| 43 | Lower pressure switch open while a higher one is closed | Call a pro |
| 21.1 | 24 volts sensed at the gas valve when there should be none | Safe checks first, then a pro |
| 22.1 | Flame proved while the gas valve is off | Safe checks first, then a pro |
| 35.1 | Modulating gas valve not communicating | Call a pro |
See all gas valve fault codes on gas furnaces across brands.