Ruud Furnace Code 1
Soft lockoutShown as: 1 blink of the green status LED, repeating
Soft lockout (one hour). On older Rheem/Ruud furnaces with a single green status LED, one blink means the control has locked gas heating out for an hour, normally after four failed ignition attempts. The manual's instruction is to reset system power and start over from the beginning.
Manual wording: “1 Blink - Soft lockout / Reset System power and start over from beginning”
Documented for: Standard (non-modulating, non-LXE, non-two-stage) furnaces with a green status LED, incl. RGRA/RGRB/RGTA/RGRS/RGTS/RGRT
Likely causes, most common first
- Four consecutive failed ignition attempts
- Flame proving problem - dirty or failing flame sense rod, igniter, or gas supply issue
What you can safely check yourself
- Check that the gas shutoff to the furnace is on.
- Check and replace a dirty air filter.
- Reset power once at the furnace switch or breaker to clear the lockout.
When to call a technician
If the furnace locks out again, the ignition system (igniter, flame sensor, gas valve, gas pressure) needs a technician.
A Ruud furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Installation Instructions for Upflow & Downflow/Horizontal High Efficiency Condensing Gas Furnaces - RGRA/RGRB/RGTA/RGRS/RGTS/RGRT Series (92-24161-16-19) (Rheem Manufacturing Company, RGRA/RGRB/RGTA/RGRS/RGTS/RGRT 90+ condensing furnaces using the UT Electronic Controls 1028-928 integrated furnace control; BLINK CODES (GREEN LED) block on the troubleshooting chart, page 56) · checked 2026-08-25
- Standard Furnace Diagnostic Flash Codes (TP0002) (Rheem Manufacturing Company (Ruud brand), Standard (non-modulating, non-LXE, non-two-stage) gas furnaces with a green status LED) · checked 2026-08-25