Goodman Furnace Pressure Switch Problems

The furnace is a complicated device, and Goodman furnaces come with many features that provide safe use for a long time. The pressure switch is such a feature, and it ensures that gases produced throughout the combustion process go away from your home and don’t go back into the system (it’s known as “back-drafting”).

Backdrafting can make the harmful gases generated by the combustion process go into your house’s air supply. It can also lead to small explosions in the heat exchanger, a fundamental part of your furnace.

How does the pressure switch reduce the risk of back drafting?

It’s essential to understand how does the pressure switch affects back-drafting to figure out what to do when you deal with Goodman furnace pressure switch stuck open:

• The furnace generates gases (some are harmful) throughout the heat-generation process.
• The draft inducer motor collects the gases from the heat exchanger and makes them get out of the house through a flue pipe.
• The pressure switch regulates the draft inducer for the approprwiate elimination of the gases. When the draft inducer isn’t working correctly, the pressure switch closes for completing the circuit.
• When the draft inducer motor has issues, the pressure switch opens (or “turns off), shutting down the furnace, so it doesn’t ignite until the problem isn’t solved.

The open pressure switch is a positive aspect and shows that the furnace’s safety features are running and reducing the risk of harmful gases going back into the house. When your goodman furnace displays an error informing that the pressure switch is stuck open or stays open, the pressure switch could have a problem.

What to do when the Goodman furnace pressure switch has issues?

Goodman furnaces come with a display panel with a built-in trouble-code that utilizes successive flashing LED lights for informing about issues. Even if the lights are incredibly helpful, you still need to troubleshoot your unit to discover the problem’s nature. Three consecutive flashing lights on your goodman furnace inform about the pressure switch circuitry having trouble. You have to troubleshoot the switch to identify the cause of the malfunctioning. Here are the steps to take:

Step 1

You begin with disconnecting the electrical power from the furnace. You turn it off at the breaker panel.

Step 2

You continue removing the screws securing the front panel onto the furnace, placing the board to the side.

Step 3

Look carefully to identify the pressure switch tubing that connects the induced draft blower and the furnace. The tubing is black and has good flexibility.

Step 4

Try to pull the tubing off the blower, tracing it to the pressure switch. You also have to take the tubing off the pressure switch.

Step 5

You have to remove any debris or dirt collected inside the tube; you blow the tubing out. After you’re done, you can make the connection between the tubing,  switch, and blower once again.

Step 6

Don’t forget to look at the electrical wires coming out from the switch; some lousy connections could be the culprit. When the cables aren’t safely plugged into the switch, you should press them in until they connect entirely.

Step 7

Now it’s time to plug the furnace on and wait a bit until it starts running. If the lights go back, it means that the pressure switch is faulty, so you may still have to call in the professionals.

What if the Goodman furnace pressure switch is stuck closed?

Sometimes, the control board will sense a request for heat from the thermostat (24VAC on the “W” terminal), so it will check to determine if the pressure switch is how it’s supposed to be, open or non-energized.

If the control board identifies the switch as already closed, it will cease the ignition phase and warn with an error code or attempt to run a couple of times. If not succeeded, it will flash the error code, according to the model of the furnace.

Therefore, a control board that identifies the pressure switch as closed before turning on the inducer will also determine a problem to stop ignition for safety reasons. It would help if you saw what makes the switch remain closed. Water in the hose or hoses that go to the switch, water in the switch could generate the problem sometimes.  A defective switch could cause the whole problem too. Sometimes, a short in the wiring may be the reason and even a poor control board (less likely, though).

How should you clean the tubing?

When the pressure switch is stuck, the plunger may not pull in entirely, and it could only bob around as the pressure increases in the furnace. Use a wire brush and a cloth to remove any blockages and debris from the secondary exchange and the inducer. Put aside the drain tubing and clean it very well and blow out on it. As you’re blowing out the drain tubing, you should also blow in the secondary exchanger for keeping the pressure. Don’t forget to make adjustments for the condensation trap so that water gets to the drain, as the furnace gases could the trapped.

You can attempt to solve the situation, and take a look at the pressure switch. Does it open and close? You should use an ohmmeter when you’re blowing/sucking on the pressure hose.

Replacing the pressure switch with a manual switch for some time could also be a solution, but you need to make sure that the switch is open and make the request for heat afterward. Once the inducer begins to operate, you may close the switch. Your furnace is supposed to run without any errors until you eliminate the request for heat. You will need to call the professionals to adjust the thermostat because the control board identifies the prolonged time of closing the pressure switch as an error, giving the “failed to close” code.

Side note

Always make sure that you correctly identify the error code on your Goodman furnace. Three blinks mean that the pressure switch didn’t manage to close, whereas two blinks mean that it’s stuck closed.