Goodman GMEC960803BN Error Code Red 6 Flashes: Pressure Switch Cycle Lockout
What Does Code Red 6 Flashes Mean?
Six red flashes on the Goodman GMEC960803BN's Integrated Control Module indicate a pressure-switch cycling lockout — the pressure switch opened five times during a single heating cycle. Each time the switch drops out mid-cycle, the board stops the burners for safety; after the fifth event in one cycle it locks out rather than continuing to retry.
Unlike a switch that never closes at all (red 3 flashes) or is stuck closed (red 2 flashes), this fault means the switch does close and let the furnace start, but draft keeps dropping just enough during the cycle to reopen it. The classic causes are an intermittent or partial venting restriction and a leaking or loose pressure-switch tube that bleeds off vacuum. Marginal draft from a long or restrictive vent run can also cause it.
Because draft is fluctuating during combustion, this is a high-severity venting-safety lockout. It is closely related to the other pressure-switch codes on this board, and clearing the lockout without correcting the marginal draft will typically just let it recur on the next cold day.
What You'll Notice
- The furnace starts and runs briefly several times, then shuts down completely with six red flashes
- Heating that drops out repeatedly within the same call before locking out
- The problem is worse in high wind or when the vent is partially obstructed
- You may hear the inducer and burners cycle on and off multiple times before lockout
- The furnace will not restart until the lockout is cleared and the cause is fixed
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Excessive venting restriction | Most common | ✗ Call a pro → |
| Leaking pressure switch tubing | Most common | ✗ Call a pro → |
How This Is Diagnosed
Because the switch is opening repeatedly under load, a technician looks for anything that lets draft fluctuate: partial vent or intake restriction, water or debris in the pressure-switch tubing, a loose or cracked tube, and marginal vent length or slope. The pressure switch is tested against the specified draft, and the vent system is checked for restriction that only shows up while running. This venting and pressure-switch work is a professional repair.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The furnace starts several times then locks out with six red flashes
- The dropouts get worse in windy weather or with a partially blocked vent
- The lockout returns after being cleared
- Any diagnosis involving the pressure switch, its tubing, or the vent system
Frequently Asked Questions
What does pressure switch cycle lockout mean?
It means the pressure switch opened five times during one heating cycle, so the furnace locked out for safety. The switch is closing to allow startup but draft keeps dropping enough to reopen it — usually from a partial vent blockage or a leaking pressure-switch tube.
Why does this happen more on windy or snowy days?
Wind and snow can partially obstruct the vent termination and cause draft to fluctuate, which makes the pressure switch open and close during the cycle. Once it opens five times the board locks out. The vent should be inspected by a technician.
✓ Verified against manufacturer service manual — March 2026