Goodman furnace 4 flashes: Open Primary Limit Switch
Try DIY first, then call a pro
What does 4 flashes mean on a Goodman furnace? The high-limit opened — the furnace overheated. The circulator blower runs until the limit closes. Code: four short flashes.
Before you touch anything: the six signs that mean stop troubleshooting and call a pro →
Homeowner checks for Goodman furnace 4 flashes
These are limited airflow checks, not a complete furnace repair. If you smell gas or a carbon monoxide alarm sounds, leave the home right away without operating any switches, then call the gas utility or 911 from outside. Never bypass a safety switch or reset the furnace over and over.
- Turn the furnace off
Set the thermostat to off, then turn off the furnace's power switch near the unit. Do not open the electrical panel or any furnace compartment beyond the filter slot.
- Replace the filter with the same size and type
Slide out the accessible filter and check the size printed on its frame. Fit a replacement of the same size and type, following the airflow direction marked on the filter slot or in your unit's instructions. Keep the furnace off until the filter is in place.
- Open and clear room vents
Walk through the home and make sure every supply register and return grille is open and not blocked by furniture, rugs, or curtains. Do not reach into the ducts.
- Restore power and stop if the code returns
Turn the power switch back on and set the thermostat to call for heat once. If the same code comes back, leave the furnace off and call a licensed HVAC technician instead of resetting it again.
Repeated overheating cooks heat exchangers (a CO-risk precursor). Recurring code 4 = service call. DIY part cost: $5–25 / $10–25 — a pro visit for this class of fault typically runs $150–350.
What causes it (in order of likelihood)
- Dirty filter or restrictive ductwork (official first cause) DIY-CHECKABLE
- Faulty limit switch TECH
- Weak blower motor or failed capacitor TECH
Parts referenced by this code
Always match parts against your model's parts list — part numbers vary within a series.
Questions about this code
What does 4 flashes mean on a Goodman furnace?
The high-limit opened — the furnace overheated. The circulator blower runs until the limit closes. Code: four short flashes.
How do I fix Goodman furnace 4 flashes?
With the power off, replace an accessible filter with the same size and type and open every supply and return vent. If the code comes back, stop resetting and have a technician check airflow and the limit.
How much does it cost to fix Goodman furnace 4 flashes?
A clogged filter may cost only a replacement filter. A recurring overheat could involve the limit switch, blower motor, capacitor, or ductwork, so the price depends on a technician's findings.
Related symptoms
These symptoms can appear alongside this code. The link is an association, not a diagnosis, and code meanings vary by brand, model and control.
Applies to
GMS8 · GDS8 · GHS8 · GMSS96 · GMH8 · GDH8
Different Goodman generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Verified against Goodman GMS8/GDS8/GHS8 Service Manual (RS6612006), p.42 — “four short flashes followed by a pause”
Verified against Goodman GMSS96 Service Manual, p.32
Last verified 2026-07-06 · page updated 2026-10-07 · how we verify
Related Goodman furnace codes
These codes use the same single red led — flash codes system.
| Pattern | Meaning |
|---|---|
| 3 flashes | Pressure Switch Stuck Open |
| 5 flashes | Flame Sensed With No Call for Heat |
| 2 flashes | Pressure Switch Stuck Closed |
| 6 flashes | Open Rollout Limit Switch |