3 red flashes: Low-fire pressure switch stuck open
Homeowner checks
The inducer ran but the low-stage pressure switch never closed — the vent could not pull enough vacuum. The manual lists a faulty switch, bad tubing or wiring, a failed inducer relay, or a restricted/over-long vent run.
From the table: Red-LED chart — two-stage 96% furnaces — source: Goodman GCEC960803BN Installation Instructions, Troubleshooting Chart, pp. 55-56 (read the document, fetched 2026-10-30). Covers: GMEC96 / GCEC96 and their Amana twins — the current two-stage condensing furnaces with a green/amber/red LED trio on the board.
Here is the whole problem in one paragraph. Goodman's current two-stage chart (GMEC96/GCEC96) says 3 red flashes = low-fire pressure switch stuck open: the inducer ran, and the switch that proves draft never closed. Goodman's older single-LED chart (PG-series instructions) says 3 flashes = pressure switch stuck closed: the switch was already closed before the cycle began. Bloggers copy one chart or the other, never say which, and Goodman owners get advice for the opposite failure.
Which one is yours?
Count the LEDs. Three of them — green, amber, red — on a 96% two-stage furnace: the stuck-open meaning (the answer box above) applies. One diagnostic LED on an older single-stage furnace: the stuck-closed meaning applies, and the fix path changes completely — a switch closed at rest is a parts diagnosis (faulty switch or wiring, per the manual), not a venting hunt.
Still not sure? The model number decides it: GMEC96/GCEC96 prefixes take the first chart. And the chart inside your blower door settles it beyond argument.
Homeowner checks — the safe list:
- Go outside and look at the vent and intake pipes. Snow, ice, leaves, a nest, or a mulch pile against the terminal can cause exactly this code.
- On a condensing (90%+) furnace, check the condensate drain: a backed-up drain or frozen drain line trips the same switch.
- Air filter: a starved furnace is a furnace that overheats and behaves badly in several code families.
- Make sure the blower door is fully seated after you look at the light.
If yours is the stuck-open version, work this order
The manual's causes for the GMEC96 code: faulty pressure switch, pressure-switch tubing or wiring problems, a failed inducer relay on the board, or a restricted / over-long vent run. Translated into what you can actually check: the outdoor vent terminal first (snow and debris are the classic January cause), the condensate drain second (a backed-up drain strangles the same switch on condensing furnaces), and the filter third. If the inducer is not running at all, stop — that is the relay/board end of the list, and it is a technician's.
The two rules that outrank everything on this page.
1. Smell gas? Stop reading. Leave the house and call your gas utility or 911 from outside. No code is worth diagnosing through a gas smell.
2. Never bypass a safety switch — no jumping a pressure switch, no taping a limit, no propping a rollout. Those switches are the only thing between a furnace fault and a fire or carbon-monoxide problem. This library explains codes; it does not teach repairs inside the cabinet.
Questions
Why do other sites say Goodman 3 blinks is "pressure switch stuck open," full stop?
Because for the current furnaces, it is — and most sites copy the newest chart without mentioning the older board exists. If your furnace is a 96% two-stage model, that advice is right. If it is an older single-stage unit, the same sites are telling you the opposite of your manual.
My Goodman flashes 3, pauses, and the inducer is running. Which meaning?
An inducer that runs points at the stuck-open failure — the board only energizes the inducer when it is trying to prove draft. That is the GMEC96 pattern. The stuck-closed code on the older board shows with the inducer off, because the board refuses to start.
One honesty note before the tables: codes change between control boards, sometimes inside the same brand and the same decade. Every table below names the board and the manual it was transcribed from. The chart glued inside your own blower door is the final word for your furnace — if it disagrees with this page, believe the door.