York furnace 6 red flashes: Pressure switch cycle lockout
Six red flashes means the pressure switch opened and closed too many times within a cycle. York marks it a one hour soft lockout, so the furnace releases itself and tries again.
Applies to: York, Luxaire and Coleman gas furnaces using the UTEC integrated furnace control boards documented in technical service letter ST-045-09. York marks this as a one hour soft lockout.
What it means
This is not a single draft-proving failure but a pattern of them. The switch is closing, proving draft, then dropping out during the cycle — repeatedly — until the control stops. That points at something different from a switch that will not close at all: a marginal or intermittent draft, where the furnace can prove draft momentarily but cannot hold it. York marking it a one hour soft lockout produces the familiar hourly heat pattern, and that timing is itself a clue that the fault is one of the soft-lockout family rather than a hard one.
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 weakening and unable to hold its output steadily.
- A pressure switch operating at the edge of its setpoint.
- A sensing hose partly obstructed, so pressure fluctuates.
- 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, pointing at an intermittent condition.
- Note the hourly pattern if present, which matches the documented soft lockout.
- Check the outside vent termination for partial restriction and note the weather.
- Check the condensate drain for slow drainage rather than complete blockage.
- Have the stored fault history replayed, since the sequence of codes around this one is informative.
How to fix it
- Clear the vent termination and condensate drain if either is partly restricted.
- The pressure switch, hose, and inducer are technician work.
- Have the vent system assessed properly if the restriction is not obvious. Marginal draft is harder to find than absent draft and produces exactly this code.
- Record when it happens — time of day, weather, how long the furnace had run. That information is something only the householder can supply and it materially helps.
Notes
Intermittent faults are the hardest to catch because the furnace usually works when the technician arrives. On these boards the stored fault history partly solves that, which is why clearing it before the visit is a real loss.
Related
- 3 red flashes — Pressure switch open, or first stage pressure switch open
- Fault code retrieval — How to read and clear stored fault codes on York UTEC boards
All codes for this manufacturer
York, Luxaire and Coleman furnace flash codes — every code, with what differs between models.
Not sure this is your brand?
The same count means something else on other furnaces. What 6 flashes means on every brand puts them side by side.
What the fix costs
The parts are the same as the stuck-open code — pressure switch at $150–400, inducer at $300–900 per the furnace repair cost guide — but the diagnosis costs more of the money here, because intermittent faults resist the first visit. A $75–150 diagnostic call that cannot reproduce the dropout risks becoming two diagnostic calls, which is why the stored fault history and your own notes are worth actual dollars on this code specifically. The weather-driven causes — wind at the termination, progressive icing during long runs — can cost nothing beyond a termination adjustment once identified. The expensive version of this fault is not any single part; it is paying for repeat visits while the real cause, a marginal vent restriction, goes unmeasured.
Fix it yourself or call a professional?
The homeowner job on this code is evidence collection, and nowhere in the York table is it more valuable. Record when the lockouts happen: time of day, weather, wind, how long the furnace had been running. An hourly heat pattern confirms the soft lockout; dropouts only on windy days point at the termination; dropouts late in long cycles point at progressive icing or a drain slowly backing up. Physically, stay outside the cabinet: check the termination for partial restriction and watch whether the condensate drains slowly. Everything cyclical inside — a switch operating at the edge of its setpoint, an inducer that cannot hold output — needs a manometer on the switch while the furnace runs, which is precisely the technician work a good log makes shorter. Do not keep resetting through it: draft that drops out mid-cycle is a safety margin being consumed in real time.
The same fault on other brands
On the matching Goodman GMEC96 table this count carries the same meaning — 6 red flashes, pressure switch cycle lockout — another of the code-for-code matches from the two tables' shared White-Rodgers lineage. Most other control families do not give repeated mid-cycle dropouts their own code, folding them into the general stuck-open fault instead, which loses exactly the information York preserves here: that the switch can close and cannot stay closed. The pressure switch code index puts all 47 codes across twelve families side by side.
What this looks like
From the outside, this usually shows up as the furnace starts and stops in short bursts — that walkthrough covers what to check in order, and when it stops being a homeowner job.