Goodman GMS8 troubleshooting

Goodman GMS8 furnace troubleshooting

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Goodman gms8 furnace stands out with some special features such as blower resistant to corrosion, tubular heat exchanger, and long-lasting hot surface mini-ignite. The self-diagnostics on the control board is also a feature that requires attention. The AFUE rating is 80%, which describes it as a low-efficiency furnace compared to new models.

What is the AFUE rating?

AFUE refers to the gas furnace’s ability to turn fuel into energy. A furnace with an 80% AFUE rating will transform 80% of the energy it uses into heat. As the 20% is utilized throughout the heating phase, the higher the AFUE rating, the higher the energy efficiency. New models have at least 78% AFUE rating, with mid-efficiency models like Goodman gms8 furnace with AFUE rating from 80 to 85%. The high-efficiency models impress with AFUE rating ranging from 90 to 97%.

Troubleshooting

Should you have problems with your Goodman gms8 furnace, you need to be meticulous and check every step carefully while paying attention to various factors. Keep reading for the details:

No led flashing

Not all troubleshooting will cause the led flashing, and there are several signs signaling problems for your Goodman gms8 furnace. Your Goodman gms8 furnace won’t operate, and no 115-volt power or no 24-volt power to the built-in control module could be the issue. You need to make sure that you give 115 and 24-volt power to the unit build-in module. Keep in mind to turn the power off before making any repairs.

Sometimes, the built-in control module diagnostic led doesn’t give any signal, and a circuit breaker or a blown a fuse could the cause. You will have to check the build. It controls module fuse, replacing it if required. Also, take a look as there could be shorts in 115 and 24-volt circuits that need fixing. As a solution, you should replace the built in control module fuse with a 3a automotive fuse.

If the build-in control module develops an internal fault, your unit could not operate as well. The solution will be to replace the faulty built-in control module, turning the power off before repairs. It’s wise to go over the “electrostatic discharge” part of the manual.

Led 1 flash

If your unit fails to operate and you see the 1flash code, your furnace may be lockout because there were too many ignition attempts (1 total) and “retries” (3). The unit cannot make a flame, with the lousy igniter, no gas burners, or improper orifices as possible causes. Igniter alignment, coated/oxidize, or faulty connect flame sensor could cause it too. You have to identify and adjust the gas interruption, replacing or realigning the igniter. You also have to take a look at the flame sense signal, sanding the sensor if it’s oxidized or coated. Needless to say, you should turn the power off before any repairs, handling the fragile igniter carefully. Use some steel wool for cleaning the flame sensor too.

When led 1 is flashing, the auxiliary limit could be open as the flame ceased. The gas supply could be interrupted, and the burner flames could be lacking due to low gas pressure or limited flow. You will have to make sure that the flue piping isn’t blocked in any way. The length, elbow, and termination should be correct too.

Not enough conditioned air over the heat exchanger could also cause the led1 flashing. Incorrect circulator blower speed, blocked filters, blocking ductwork, or faulty circulator blower could also cause the problem. You need to see the circulator blower speed and performance, adjusting the speed and even replacing the blower if necessary.

Led 2 flash

When your unit didn’t operate and led 2 is flashing, the pressure switch circuit could be off. It’s possibly that the induced draft blower pressure switch contacts are touching, in which case another draft blower pressure switch will solve the situation.

If the built in control module diagnostic led will flash two flashes, the induced draft blower doesn’t run at all as there are shorts in the pressure switch circuit. It would help if you fixed the short, using the right replacement part.

Led 3 flash

When the induced draft blower is running, but the unit isn’t operating, the pressure switch circuit may not be closed. The pressure switch hose is not connected correctly, but it could also be pinched or blocked. Take a look at the pressure switch hose, making repairs if needed. Always stay safe by turning the power off before addressing any issues.

When the built-in control module diagnostic led is flashing three flashes, and the draft blower is running, the induced draft blower could be weak or even blocked. Take a look at the fuel to see if there’s right length, termination, elbows, or blockage.

Improper pressure switch setpoint and fault switch contacts could be the causes too. Adjusting the pressure switch set point or the contact motion could solve the trouble.

Not wiring correctly or loose wiring may cause the flashing, so you will need to adjust or tighten the wiring. Replacing the pressure switch with the correct part could be necessary too.

Led 4

The unit doesn’t run, whereas the circuit blower is functioning without stopping. The primary limit circuit could be open, as there’s not enough conditioned air over the heat exchanger. You should see the ductwork and the filters if they’re causing blockage or not. Make sure you eliminate the obstruction and clean the filters, turning the power off before any repairs.

Sometimes, the built-in control module diagnostic led is flashing four flashes, signaling the limit circuit’s opening. You should pay attention to the circulator blower performance and speed, adjusting the speed, and even switch to a new blower if needed.

Led 5

When the furnace doesn’t function, but the induced draft blower and circulator blower are running without stopping or the built-in control module diagnostic if flashing 5 flashes, the flame was turned on without heat request. The flame sense circuit may have developed a short to ground, so you will need to adjust short at the flame sensor or in the flame sensor’s wiring. Always turn the power off before any repairs.

Led 6

The unit isn’t running, or there are 6 flashes for the control module diagnostic led, the rollout limit could be open. The flame rollout, blocked fuel, air inlet pipe, misaligned burners, or faulty induced draft blower could be the leading causes. Wrong or loose wiring could be the culprit too. See if the burners are correctly aligned and look at the air inlet piping and fuel to spot any blockages. Make sure you also observe the elbows, length, and termination, adjusting if needed. Also, see the induced draft blower for the performance and get a new one if required. You may also have to adapt or tighten the wiring, replacing the induced draft blower with the correct part.

Led 7

Even if your unit is running, the control module diagnostic led flashes 7 times, as the flame sense microamp signal isn’t powerful. The flame sensor could be oxidized or coated, in which case you will need to sand it. Use some steel wool for cleaning the flame sensor.

A flame sensor that isn’t correctly placed in the burner flame could be the culprit, so you should check the sensor to see if it’s aligned. Not adequate gas pressure and combustion air could cause a lazy flame, so control the inlet air piping for any blockage and the elbows, termination, and length. Don’t forget to compare current gas pressure to the rating plate data, making the necessary adjustments.

Continuous flashing c

Your unit isn’t running, but the induced draft blower is operating without stopping. The polarity of 115-volt power is typically reversed, so you have to go back over the wiring diagram for proper polarity.

As the control module diagnostic led flashes without stopping, the unit could be poorly grounded, so you will need to correct it. Take a look at the wiring and making any changes if necessary. Needless to say, always turn the power off before making any repairs.

One last piece of advice

If the LED is steady on, your furnace is working correctly, so no repairs, adjustments, or fixing are needed.

 

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