Save on the MARS 43373 LP PRESSURE SWITCH CLOSE 40 here with the pros at PlumbersStock. Pressure switches make contact on pressure rise/fall, which enables its switching operation. A pressure switch senses negative pressure in a furnace and shuts it down as a safety measure against harmful fumes and gas leaks.
As the manufacturer describes it, MARS Pressure Switches deliver the reliability and performance that makes them the most trusted electromechanical sensor. The MARS line of pressure switches cover many new R410A applications along with traditional pressure setting switches. It's easy to replace. Mars replacement parts can be hard to find, so contact us if you have any problems.