Carrier Furnace Error Code 43 Flash: How to Fix It

Q: What causes Carrier furnace error code 43 flash?

Error code 43 flash is caused by a pressure switch calibration fault, typically due to blocked vents, dirty air filters, faulty pressure switch hoses, or a malfunctioning pressure switch itself.

Q: Can I run my Carrier furnace with error code 43?

No, you should not run your furnace with error code 43. This error indicates a safety issue with airflow detection, and the furnace will not operate properly until the problem is resolved.

Q: How much does it cost to fix a pressure switch on a Carrier furnace?

Professional pressure switch replacement typically costs $150-$300 including parts and labor. Simple fixes like cleaning blocked vents or replacing air filters cost much less.

Q: Is error code 43 flash the same as error code 43?

Yes, Carrier furnaces display error code 43 as a flashing light sequence. Both refer to the same pressure switch calibration fault issue.

Q: How often should I check my furnace pressure switch?

The pressure switch should be inspected during annual furnace maintenance. However, you should check air filters monthly and keep exterior vents clear year-round to prevent pressure switch issues.

Abstract

Carrier furnace error code 43 flash indicates a pressure switch calibration fault with the low pressure switch. This error means the furnace's pressure switch isn't detecting proper airflow, which is a critical safety feature that prevents unsafe operation.