HVACopediaAll brands · Furnace troubleshooting
Cold air blast at start / blower never stops
What is going on
Possible causes and checks for: cold air blast at start / blower never stops.
Likely causes
- Fan switch set point or time delay wrong (on ≈140 °F, off ≈90 °F)
- DIP/jumper delay settings
More furnace guides
Take it to the job
All guides, error codes and tips work offline in the HVACopedia app.
Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.