Furnace Pressure Switch Troubleshooting

Furnace Pressure Switch Troubleshooting | Solved !

Many of us look for the tips and ticks of furnace pressure switch troubleshooting but without proper information, many don’t able to handle this because It has some critical parts, which ensures the perfect and efficient performance of the furnace system. Here we are going to discuss an overview of furnace pressure switch, types, and other related information.

What Is A Furnace Pressure Switch?

A Furnace Pressure Switch is an automatic protection feature located near the motor. This shuts off the reactor when the negative pressure created by the Draft-Induced motor is sensed. This protects your home from dangerous back drafting when the fumes from the system are re-injected into the furnace. The pressure switch protects you from many other things. For example, if there is a mechanical failure, it prevents the furnace from cycling, it signals if there is a gas leak, etc.

Different Types of Pressure Switch:

There are different types of furnace pressure switches and design depending on the use of conventional or condensation technology.

  • Single-Stage Conventional Furnace (Type-1)

    A pressure switch and a hose reactor are single-stage conventional reactors. It carries a draft of inspiration in the body of the fan.

  • A Single-Stage Condensing Furnace (Type-2)

    A single-stage condensing furnace has a pressure switch, consisting of two hoses with one for sensing pressure around the draft Inductor or burner and the other for sensing the appropriate venting pressure in the condensate collector box.

  • Two-Stage Furnace

    If there are two pressure switches, it is called a two-stage furnace.

  • Modulating Furnace

    If there are three pressure switches it is called modulating furnace.

Causes of Furnace Pressure Switch Failure

A bad switch, or a tripod switch, is a common cause of furnace errors. There are several reasons why pressure switches may not work, such as aging, which can lead to misreading and faulty furnace cycling. Let’s take a look at the causes of pressure switch failure:


Problems of Inducer Fan-
• If the Inducer fan runs at a very slow speed
• If the Inducer fan motor becomes expired dated
• If the Inducer fan is obstructed
• Water stuck in Inducer fan housing (high-efficiency furnace)


Problems from Switches-
• If the switch become expired dated or shorted
• Switch that gets jammed with dirt or dust.
• Hardening or coating pressure switch
• Broken, perforated or damaged diaphragm


Problems with the suction tube-
• If the suction tube becomes loose
• If there is a crack or hole in the suction tube


• If the cable connection becomes loose
• If the flu or chimney gets stuck

Checking Gas Furnace Pressure Switches:

Equipment / Tools to Check
Flashlight, Screwdrivers, Multimeter, Pressure switch hose (if needed)

• First set your meter to volt AC, and then turn on your furnace. Then heat it enough.
• The draft index should start at this time.
• You will see two or three wires through the pressure switch.
• lead of pressure to test a lead, touch the other lead on your meter to the ground.
• The ground must be a metal part of your furnace.
• With a two-wire pressure switch you can get 24 or more volts between the two grounds.
• If you do not get 24 or more volts running in the furnace, assume you have a pressure switch problem.

Instruction Order

STEP-1: Turn Off the Power
Turn off the disconnected switch of the furnace and turn off the power of the furnace. Turn off the furnace breaker on the service panel if there is no disconnected switch.


STEP-2: Check The Pressure Switch Hose.
Remove the main access panel in front of the furnace, inspect the hoses attached to the pressure switch, and make sure it is attached to both ends and in good condition. If the hose is cracked, it needs to be replaced.


STEP-3: Check For Hose Pipes Barriers
First, notice carefully where the pressure switch is attached to the hose. Then remove them. (If there are multiple hoses, remove them at once. Then reinstall). If there is any obstruction inside the hose, remove it.


STEP-4: Check the Hose Port
Inspect the hose port on the pressure switch with a flashlight inside. If there is any obstacle in it, remove it. Remove debris with a small screwdriver or similar tool, being careful not to put 2k in the switch body. Do not hit the blank to remove obstacles. Reinstall the hose(s).


STEP-5: Check the Furnace Cover
Make sure the ventilation slots on the furnace cover are clean of debris. Clean the vents if necessary.


STEP-6: Look For Blockages in The Vent
If the furnace is condensing type, check the vent pipe to prevent obstruction. A vent pipe is a PVC (plastic) pipe usually extending along the side walls or roof of the house.


STEP-7: Check the Resistance
Disconnect by pulling the wires connected to the pressure switch from the switch terminal. Check the resistance (ohms) with a multimeter. The value will be close to 0 or 0. The switch failed if the value is higher. At this time, it is important to replace the switch by a qualified technician.

After all, furnace is a complex machine and to troubleshoot the furnace pressure switch is not an easy task sometimes. So its better decision to consult with technicians. We are serving our customers for years with 100% dedication to make customers satisfy in Red Deer and surrounding areas. Just book us today and we would be happy to help you.

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