I am getting a pressure draft safeguard, Aux limit, or blocked vent switch code. I didn't see this code in your article, any suggestions?

Answer

Most often it means the pressure switch is bad but you could have a bad inducer fan or a blockage in the chimney. These are again the most common causes but not a definitive answer.

Updated on January 8, 2018

Original Article:

How to Diagnose Furnace Problems & Why Red Light Is Blinking
By Dan Robbins
working