Error Code No LED Signal
High

Goodman GMSS960803BN Error Code No LED Signal: No Power

TL;DR
Your Goodman GMSS960803BN has no power — the diagnostic LED is completely off. Check the circuit breaker, furnace disconnect switch, and make sure the blower door is fully closed.
Disclaimer
This article is for informational purposes only and does not guarantee the accuracy or completeness of the information provided. Always turn off power and gas supply before attempting any repairs. If you smell gas, leave immediately and call your gas company. Consult a licensed HVAC technician for diagnosis and repair. Any actions taken based on this information are at your own risk.

What Does Code No LED Signal Mean?

When the diagnostic LED on your Goodman GMSS960803BN is completely off, it means the furnace control module is not receiving power. The furnace cannot operate at all in this state.

The most common cause is a tripped circuit breaker or a furnace disconnect switch that has been turned off. The furnace also has a door safety switch that cuts power when the blower compartment door is removed or not fully seated — this is a frequent cause that is easy to overlook.

Less common causes include a blown 3A fuse on the control module or an internal control module fault. If the circuit breaker trips repeatedly after resetting, there may be an electrical short in the furnace wiring that requires professional diagnosis.

Common Causes

Cause Likelihood DIY?
No 115V power to furnace (tripped breaker or disconnect switch off) Most common ✓ DIY fix →
Blown 3A control module fuse Common ✗ Call a pro →
Door switch open or disconnected Common ✓ DIY fix →
Internal control module fault Uncommon ✗ Call a pro →

How to Fix It: Check the Circuit Breaker, Disconnect Switch, and Door Switch

⚠ Safety First
Always turn off the furnace at the power switch or breaker and shut off the gas supply before beginning. Do not proceed if you smell gas — leave the area and call your gas company immediately.

What You'll Need

Steps

  1. Turn off electrical power and gas supply Before inspecting, turn the gas shutoff valve to the OFF position (handle perpendicular to the pipe). If you smell gas, leave immediately and call your gas company.
  2. Check the circuit breaker Go to your home's electrical panel and find the breaker labeled for the furnace or HVAC system. If it is in the tripped position (middle), flip it fully to OFF, then back to ON. If it trips again immediately, stop and call an electrician.
  3. Check the furnace disconnect switch Look for a power switch on or near the furnace — it often looks like a standard light switch. Make sure it is in the ON position.
  4. Verify the blower door is fully closed The blower compartment door has a safety switch that cuts all power when the door is open. Push the door firmly until it clicks or seats fully into place.
  5. Restore gas and test Turn the gas supply valve back to ON (handle parallel to the pipe). The diagnostic LED should illuminate with a steady on signal. Set the thermostat to call for heat and verify the furnace starts.
How to Verify
The diagnostic LED should show steady on (normal operation). Set your thermostat to call for heat and confirm the furnace ignites and runs a complete heating cycle.

When to Call a Professional

Contact a licensed HVAC technician if:

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Sources

  1. Installation Instructions for *MSS9* & *CSS9* Single-Stage Gas Furnace

✓ Verified against manufacturer service manual — March 2026