How to Bypass a Pressure Switch On a Furnace

If you are having issues with your furnace, one source could be a faulty pressure switch. Well, how do you know for sure if that is the issue? Here we help you learn how to bypass a pressure switch on a furnace through a process called jumping to diagnose this HVAC issue. Before we get to that, let’s start with the basics.

What Is a Pressure Switch?

what is a pressure switch on a furnace

The pressure switch is a safety feature on your furnace. It should be located near the blower motor. It operates by sensing negative pressure coming from the draft inducer and reacts by shutting down the furnace. This mechanism safeguards against backdrafts and gas leaks.

Should I Bypass a Pressure Switch on a Furnace?

A gas furnace pressures switch bypass is a valid test for isolating whatever issue you are trying to troubleshoot. This isn’t a solution to the problem; it’ll just tell you whether or not the issue is a faulty pressure switch. Look for a clogged hose port or maybe a cracked hose coming from the draft inducer to the pressure switch as the source of the failure.

How to Jump a Furnace Pressure Switch

All you need is a little jumper wire (or regular wire will work, too). You likely have a normally open switch, and when you jump it, you are closing it. That means the furnace has to be on before you start the test. A closed configuration will prevent startup.

how to bypass a furnace pressure switch
  1. Disconnect one of the two wires from the pressure switch.
  2. Connect it to one end of your jumper wire.
  3. Turn on the furnace. Once you hear the draft inducer startup, you’re good to proceed.
  4. Connect the other end of the jumper wire to the other wire on the pressure switch.
  5. Let it run for a few minutes. If there seem to be no problems, then you can reasonably conclude that you need a new furnace pressure switch.

Remember, bypassing the pressure switch should only be a temporary setup for troubleshooting. It should not be used as any sort of permanent setup. After all, this is a safety feature, and it’s not wise to ignore the potential threats that a pressure switch protects against.

Save On Furnace Pressure Switches at PlumbersStock

Now that you have isolated the problem thru learning how to jump the pressure switch on a furnace, it's time to buy a new pressure switch. We carry all kinds of HVAC switches, as well as a huge inventory of HVAC parts. Did you know that you can find member pricing here on certain items (typically name brand, MAP priced items) if you log in? For industry professionals buying in bulk, please consider contacting us directly for extra special pricing and extra savings.

Related resources:
What Does a Pressure Switch Do?
How to Replace Pressure Switch
Furnace Pressure Switch Stuck Open or Closed
All Furnace Tutorials and FAQ's

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