Goodman furnace 6 red flashes: Pressure switch cycle lockout
Six red flashes means the pressure switch has opened and closed too many times within a cycle, so the control has locked out rather than continuing to retry.
Applies to: Goodman GMEC96 and Amana AMEC96 two-stage gas furnaces with a three-colour diagnostic LED.
What it means
This is not a single pressure switch failure but a pattern of them. The switch is closing, proving draft, then opening again during the cycle — repeatedly. The control counts those events and, past a limit, stops rather than continuing. That behaviour points at something different from a switch that simply will not close: a marginal or intermittent draft, where the furnace can prove draft momentarily but cannot hold it. Wind at the termination, a partly restricted vent, or a condensate trap that fills during the cycle all produce this pattern, and all of them are conditions that come and go rather than being consistently present.
Most common causes
- A partly restricted vent or intake, where draft is marginal rather than absent.
- A condensate drain that backs up during a cycle and clears between them.
- Wind at the vent termination disturbing the draft intermittently.
- An inducer that is weakening and cannot hold its output steadily.
- A pressure switch at the edge of its setpoint, closing and dropping out.
- A sensing hose partly obstructed, so pressure fluctuates at the switch.
- Ice forming progressively at the exhaust termination during a long run.
How to diagnose it
- Note that this is a repeated fault rather than a single one, which points at an intermittent condition.
- Check the outside vent termination for partial restriction, and note the weather — wind and freezing conditions both fit.
- Check the condensate drain for slow drainage rather than complete blockage.
- Note whether the fault happens more on long runs than short ones, which fits a condition that develops during a cycle.
- Listen to the inducer for any change in note during a run.
How to fix it
- Clear the vent termination and condensate drain if either is partly restricted. Both are within homeowner reach.
- The pressure switch, its hose, and the inducer are technician work.
- Have the vent system assessed properly if the restriction is not obvious. A marginal draft is harder to find than an absent one, and it produces exactly this code.
- Never bypass the pressure switch. An intermittent draft is still a draft problem.
Notes
Intermittent faults are the hardest to catch because the furnace often works when a technician visits. Recording when this happens — time of day, weather, how long the furnace had been running — is genuinely useful and is something only the householder can do.