Fixing a Furnace Pressure Switch

Fixing a furnace pressure switch can be a complex task that requires knowledge of the heating system and electrical components. It is important to follow proper safety procedures and consult a professional if unsure about any steps in the troubleshooting process.

To begin, as a technician, you must understand the sequence of activities required for a gas furnace to start properly. It’s pretty simple, and you should know it by heart before you consider yourself prepared to troubleshoot.

1. Power to the furnace control board
2. The thermostat signals the need for heat.
3. The inducer motor kicks on.
4. The pressure switch proves the inducer operates correctly.
5. Ignitor activates
6. A gas valve energizes
7. Flame pours across burners
8. A flame sensor proves all burners are lit.
9. The blower forces air through the ducts.

First, the inducer motor starts

The inducer motor activates when the flame is turned on, creating a negative pressure or airflow that cleans the air during combustion, improving efficiency. Seek professional intervention for furnace repair in Manhattan right away.

Next up, the furnace pressure switch activates

The furnace pressure switch should activate if the inducer starts and works properly, and if it fails, the control board will cease delivering electricity to the inducer motor, effectively shutting it out.

How to Troubleshoot a Furnace Pressure Switch

The inducer motor is working properly, but the pressure switch is not closing. To check if the switch is closing, one lead should be placed on the incoming terminal and the other on the outgoing terminal. Another method is to test the leads across the two terminals. When the switch is open, it will report 24 volts, but when it is closed, it will see 0 volts. The pressure switch does not shut until the inducer motor starts and produces the suction required for the pressure switch to close.

Furnace Pressure Switch Not Closing

The inducer motor produces vacuum when the manometer’s hose is connected to the pressure switch tubing’s collecting chamber, and the manometer shows induced draft increasing. Low pressure is -0.4′′ wc.

Five easy things to check:

Let’s have a look at some of the possibilities here. Some of the more typical reasons behind furnace pressure switches failure or failure to shut off enough to enable the remainder of the system to fire up are as follows:

1. A blocked pressure switch port on the collecting chamber
2. A blockage in the flue
3. A burst or trapped diaphragm
4. The pressure switch hose has been damaged.
5. There is water in the pressure switch hose.

A clogged port on the collection chamber to the pressure switch

Clean the port with a small wire to remove any calcium deposits, dirt, or debris, allowing air to flow. Reach out for professional furnace repair in Queens for better result.

An obstruction in the flue pipe

Bees, wasps, and birds like to build their nests in and around the flue pipe, so it is important to check the roof vent if the furnace hasn’t been run yet.

A ruptured or stuck diaphragm

The pressure switch can fail due to a stuck diaphragm or a ruptured one, so it is important to replace it now to avoid surprises.

Breathing lightly into the hose can help troubleshoot a furnace pressure switch. Since pressure switches are almost impossible to rebuild, a new switch should be ordered.

A damaged pressure switch hose

Rats can chew holes in hoses, so extra tubing should be kept in service vans for cases like this.

Moisture in the pressure switch hose

Water can get stuck inside the tubing leading to the pressure switch, so try draining it by unplugging it from the port and having a bucket handy.