Goodman GMSS920803BN Error Code No LED Signal: No Power
What Does Code No LED Signal Mean?
On the Goodman GMSS920803BN, the Integrated Control Module signals its status through a single diagnostic LED that flashes coded patterns. When that LED shows no signal at all, the board itself is receiving no power. Either the 115-volt supply to the furnace is missing, or the 24-volt output from the transformer to the control module is absent. With a dead board, none of the ignition sequence can run, so the furnace does nothing when the thermostat calls for heat.
Goodman lists three underlying situations for a dark LED on this single-stage furnace: no 115-volt power reaching the furnace (a tripped breaker, an open disconnect switch, or an open blower-door interlock), a blown 3-amp fuse on the control module, or an internal fault within the module itself. Only the first situation is something a homeowner can safely check. The blown fuse and the internal board fault are service items, and a blown fuse usually means there is a short somewhere in the low-voltage wiring that has to be found first.
A dark LED is different from the other power-related indications on this same board. A continuous rapid flash means the board is powered but has detected reversed line polarity, and a 6-flash pattern can involve a blown control-module fuse only after the board has powered up and detected a rollout or safety-circuit problem. A completely dark LED means the module never energized at all.
What You'll Notice
- The diagnostic LED on the control module shows nothing — no flashing and no steady glow
- The furnace does not respond in any way to a thermostat call: no inducer hum, no igniter glow, no blower
- The furnace breaker may be found tripped, or the disconnect switch near the unit may be off
- The blower access door may be loose or not fully seated against its safety interlock plunger
- A recent power outage, storm, or electrical-panel work may have preceded the dead board
Common Causes
How This Is Diagnosed
The cause is isolated from the outside in, starting with the power sources a homeowner controls. First the furnace circuit breaker is confirmed ON (a tripped breaker sits in a middle position and must be pushed fully OFF before it will reset), then the furnace disconnect switch, and then the blower-door interlock, which opens the 115-volt circuit whenever the access panel is not fully closed.
If line voltage is confirmed present at the furnace but the LED is still dark, a technician measures the 24-volt transformer output and inspects the 3-amp control-module fuse. A blown fuse usually indicates a short elsewhere in the low-voltage wiring that must be located before the fuse is replaced. If power and fuse are both good and the LED stays dead, the Integrated Control Module itself is considered failed.
How to Fix It: Check the Breaker, Disconnect, and Access Door
What You'll Need
Steps
- Turn off electrical power and gas supply first Even though the furnace appears dead, switch the furnace circuit breaker to OFF and turn the gas shutoff valve to the OFF position (handle perpendicular to the pipe) before touching the unit. If you smell gas, leave immediately and call your gas company from outside.
- Inspect and reset the circuit breaker At the electrical panel, find the breaker labeled for the furnace. A tripped breaker often rests in a middle position. To reset it, push it firmly to OFF, then back to ON. If it trips again immediately, stop and call a professional — that points to a fault, not a nuisance trip.
- Check the furnace disconnect switch Most installations have a separate switch (it looks like a light switch) on or near the furnace. Confirm it is ON. This switch is sometimes turned off during cleaning or by mistake and is an easy thing to overlook.
- Reseat the blower access door The furnace has a door safety interlock that cuts 115-volt power whenever the blower door is not fully closed. Remove the door, check that nothing obstructs it, and reinstall it so it presses firmly against the interlock plunger.
- Restore power and gas, then test Turn the gas supply valve back to ON (handle parallel to the pipe) and switch the breaker to ON. Watch the control-module LED — it should light either steady for normal, or a flash code if another fault is present. Then set the thermostat to call for heat.
When to Call a Professional
Contact a licensed HVAC technician if:
- The LED stays completely dark after you have confirmed the breaker is on, the disconnect is on, and the door is seated
- The furnace breaker trips again immediately every time you reset it
- You find a blown fuse on the control board, or the board shows scorching or a burnt smell
- Line voltage is present at the furnace but the board still will not power up
- You are not comfortable working inside the electrical panel
Frequently Asked Questions
Why does my Goodman GMSS920803BN have no lights at all on the control board?
A completely dark diagnostic LED means the Integrated Control Module is getting no power. The most common causes a homeowner can address are a tripped breaker, an off disconnect switch, or a blower door that is not fully closed against its safety interlock.
I reset the breaker and the LED is still off. What now?
If the breaker, disconnect, and access door are all confirmed good and the LED remains dark, the likely causes are a blown 3-amp fuse on the control board or an internal board fault. Both require a technician, and a blown fuse usually points to a wiring short that must be found first.
Is a dead furnace board dangerous?
A board with no power will not run the furnace, so there is no combustion risk from the code itself. However, a breaker that repeatedly trips or a blown fuse points to an electrical fault that should be diagnosed rather than repeatedly reset.
Sources
✓ Verified against manufacturer service manual — March 2026