Goodman Furnace 3 flashes: Pressure switch stuck open
Updated October 2026 · Sourced from Goodman documentation
The pressure switch did not close within 5 minutes after the induced draft blower started, so the control goes into a 1 hour lockout and then retries on its own. The manual lists a disconnected pressure switch hose, a faulty switch or wiring, or restricted intake or flue piping.
Is it safe to keep running? No. Turn it off and get it checked. Call a licensed technician. Venting and pressure switch problems are combustion safety issues.
3 flashes at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| 3 flashes Diagnostic LED seen through the blower door window | Pressure switch stuck open | Goodman GMS8 / Amana AMS8 / GDS8 / ADSS8 80% single-stage gas furnaces (older flash-code control) |
Check this first
Only steps a homeowner can do safely. Do not open electrical panels or the burner area.
- Look outside at the furnace vent and intake pipe ends. Make sure snow, leaves or a nest are not blocking them. Look only, do not touch the pipes.
- Look at the condensate drain line and trap (if you can see it without removing any panel) for a clog, kink or standing water.
- Turn the furnace power off at the switch or breaker, wait one minute, then turn it back on to see whether the code returns.
🛑 Stop and call a licensed pro if
- Call a licensed technician. Venting and pressure switch problems are combustion safety issues.
- You smell gas. Leave the house, do not touch switches, and call your gas utility from outside.
- Flame rollout, limit or pressure switch codes that come back after one reset.
- Anything involving the control board, gas valve, flame sensor, igniter or venting.
- A carbon monoxide alarm sounds. Get everyone outside and call 911 or the fire department.
Safe first steps for any Goodman code
- Count the LED flashes through the blower door window before you switch anything off. Cutting power can clear the code.
- Replace or clean the furnace air filter.
- Check the thermostat: correct mode, set above room temperature, and fresh batteries.
- Make sure the furnace power switch and breaker are on. If the furnace has locked out, turning the power off and back on once restarts it.
- Make sure the gas valve is in the ON position, following the lighting instructions on the furnace label only.
- On high-efficiency furnaces, look at the outside vent and intake pipes for snow, ice, leaves or nests (look only, do not take pipes apart).
Source: Goodman GMS8/AMS8/GDS8/ADSS8 80% Single Stage Service Instructions RS6612006 (July 2013), pp.37-39. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
Shaun Cain · Certified HVAC & Refrigeration Technician · Ask an HVAC technician