Goodman Furnace Error Codes – Troubleshooting Guide

Goodman furnaces have a display panel with a built-in trouble-code that uses LED lights to show the homeowner that there is a malfunction of some sort.

What do these error codes mean and is there anything that you can do to fix these problems? Here is everything that you need to know. 

Goodman Furnace Error Codes

Single LED flash; steadily on

Your furnace is not able to operate as it can’t detect the signal coming from the thermostat.

The problem is, most likely, with the thermostat and not the actual heating unit. So, you would have to troubleshoot the ‘brain of the system’.

  • Replace the batteries and make sure that the thermostat is getting power.
  • Remove the cover. If the inside seems dirty, use a soft brush to gently clean the thermostat.
  • Tighten up the terminal screws, if they seem a bit loose (do not overtighten them though).
  • If the wires look corroded, then you would have to replace the thermostat.

Tip: the location of the thermostat can affect the device’s performance. Make sure that it is not exposed to direct sunlight, heat sources, or drafts.

Read: Why Does The Room Temperature Not Match The Thermostat Setting?

Single LED flash; flashes on and off

Your furnace has been locked out. In an hour, the system is going to reset itself.

This might have happened because there were too many ignition attempts. A defective flame sensor, faulty igniter, or a limit switch response might be to blame.

In a lot of cases, you’ll be able to get the furnace out of lockout by resetting the unit. Simply turn the power off, wait for around 20 seconds, and then turn it back on.

However, the issue might persist, even after you had reset the furnace. Professionals would definitely recommend tackling the root cause.

Here are a few other things that you can do:

  • Clean the flame sensor or replace it, if necessary. Soot can easily be removed by cleaning, but if you see cracks or other signs of damage, then the sensor might have to be removed.
  • Change the air filter. The system can’t have an adequate airflow with a clogged filter which, in its turn, will lead to a tripping limit switch.
  • Inspect the vent pipes and clean them, if necessary. Clear any blockage and get rid of the debris.

At times, the blockages might be impossible to get rid of. In such a case, an HVAC expert would have to replace the pipe section that had been clogged.

Read: Furnace Filter Airflow – What You Need To Know?

Two LED flashes

There is either a problem with the draft blower or there is an issue with the pressure switch circuit.

The pressure switch helps ensure that the gases created during the combustion process exit your house and do not stay in the system.

The switch ‘monitors’ the draft blower to make sure that the component is safely getting rid of all these dangerous gases. However, if there is an issue with the draft blower, the pressure switch will open and stay like that (this will shut the furnace down).

  • Check the flue pipe to ensure that it’s not obstructed.It is located either on the roof or on the side of the house. The pipes can easily get clogged with dirt, leaves, and even feathers, so simply clean the components.
  • The inducer motor and the switch are connected via a pressure switch hose. If the thing is damaged, the switch won’t be able to correctly ‘read’ the blower motor.As a result, it will stay open.The hose is not something that you can easily fix on your own, so make sure to call a professional.
  • Finally, the actual pressure switch might be faulty.The component should be tested with a multimeter and then replaced, if necessary.

Read: American Standard Furnace– Troubleshooting Guide

Three LED flashes

Either the draft blower is operating, when there isn’t such a need, or there is an issue with the pressure switch (it’s open).

Follow these steps to troubleshoot the switch:

  1. Turn the power off.
  2. Find the furnace’s front panel and remove the screws.
  3. The draft blower is connected to the switch via black, flexible tubing.
  4. Pull the tubing off the draft blower and follow it to get to the switch.
  5. Pull the tubing off the switch.
  6. You can choose to blow right into the tubing. This will help remove any debris.
  7. Reconnect the tubing to the pressure switch and the blower.
  8. Inspect the wires for corrosion or a bad connection. If it’s possible, fix the connection.
  9. Turn the furnace on. The LED signals should go away (if you can still see the flashes, it looks like the switch would have to be replaced).

Four LED flashes

The furnace has a primary open limit circuit. 

Usually, you will be able to easily fix the issue simply by changing the air filter.

You can also try tightening the wiring and checking the flue for any blockages. 

Tip: do not overtighten the wires, screws, or any other fittings. It can deform the components and cause a wide range of serious issues. 

Read: Why Does My Furnace Filter Get Dirty So Quickly

Five LED flashes

Your Goodman furnace had sensed a flame without a call for heat.

Check for an open or leaky gas valve. You can use an electronic gas sniffer or soap bubbles.

A lingering burner flame might also be the issue.

Before proceeding with any manipulations, make sure that the furnace is off and that you have turned the gas off at the valve.

Seven LED flashes

This indicates a low flame.

Your unit might have low gas pressure. If that’s the issue, you would have to adjust the pressure.

Fact: the minimum and maximum gas supply pressures to the furnace are 5″ WC and 10.5″ WC (natural gas) and 11″ WC and 13″ WC (LP gas). 

If you want to try to adjust the pressure on your own, you would need a U-tube manometer.

  • Shut the gas off and remove the input pressure tap plug.
  • Connect the manometer to the pressure tap.
  • Turn on the gas supply and note the line gas pressure (adjust, if necessary). 
  • Shut the gas off, remove the manometer.
  • Replace the plug, turn the gas on, and check for leaks.

The issue might as well be with a coated flame sensor. You would have to remove the sensor and clean it with very light grit sandpaper. 

Eight LED flashes

There is an issue with the ignitor circuit. 

  • Check the breaker to make sure that it had not tripped.
  • Inspect furnace connections – some connections can get loose because of the constant vibration.
  • Check the ignitor. If you have had your furnace for quite a while already, the chances are high that the ignitor simply got worn out over time. 

Nine LED flashes

The high-stage pressure switch is not closing. This is causing the high-stage draft blower to run.

Follow the instructions provided above for the ‘two LED flashes’.

If, for some reason, you would have to install a new pressure switch, make sure to install the component in a vertical position.

Diaphragms can’t be activated as easily if they have to fight gravity. The chances are high that the furnace will work for a bit, but you would still have to fix the problem a few days later.

So, when mounting the pressure switch, do it vertically.

Tip: ensure that there are no dips in the hose, as this is where water will accumulate, causing the switch to fail in a few days. 

Continuous LED flashing

Your furnace has a reversed polarity.

In a lot of cases, a unit with a reversed polarity will continue to work. But the main problem with such a furnace is that the unit will remain energized, even when it is turned off.

This can short-circuit the device and is overall not safe (such units can easily shock you).

If you have no idea how to work with wiring, then you should definitely invite a professional to fix the problem.

However, if you have the wiring diagram and you feel comfortable working with electricity, then you can try to correct the wiring polarity yourself. 

What does a solid red light on a Goodman furnace mean?

A solid red light might mean two things – that the board is normal and it’s simply waiting for a heat call or that the burner is running but the unit is not getting a call for heat.

In any case, you should check the thermostat. To troubleshoot this device, follow the instruction provided in ‘single LED flash’.

Read: Why Does Home Thermostat Say HEAT ON But There Is No Heat?