1 blink Soft lockout (failed ignition)

What the control is telling you

Green STATUS LED blinks once: the control has given up after 4 ignition attempts and is in a 1-hour soft lockout; it ignores the heat call (W) until reset. The chart says to kill power 30 s to reset; the Sequence of Operation says 5 s (or cycle W off/on) and also 5-10 s at the thermostat or disconnect - see notes.

Applies to: Rheem (-)GRC upflow and (-)GTC downflow/horizontal 90 Plus condensing gas furnaces (UT Electronic Controls 1012-925 / 1028-928 and Invensys ICC-H1MC7-01 IFC); Rheem 90RJ and 90TJ 90 Plus condensing gas furnaces (UT Electronic Controls 1012-925 or Invensys ICC-H1MC7-01 IFC, hot surface ignition)

Likely causes

• No or low gas supply / wrong manifold pressure
• Igniter not heating (HSI open, cracked, mis-placed) or spark electrode not sparking (DSI)
• Weak or no flame signal - dirty flame sensor rod, poor ground, L1/Neutral reversed
• Gas valve not opening (wiring, manual switch OFF, open aux. limit or drain pressure switch)
• Restricted orifice or poor flame carry-over across burners

Test and repair steps

1. Reset shut off main power to the furnace, wait 30 seconds, restore power and make a fresh heat call.
2. Watch the cycle the inducer pre-purges, the igniter heats (HSI glow or DSI spark), then the gas valve is powered for about 7-8 s per trial; the system tries 4 times and the blower + inducer run 180 s between the 2nd and 3rd attempts.
3. No glow/spark HSI - check igniter is connected, wires, resistance (replace if open, too low or too high), cracks and placement; DSI - check electrode wire/connections, gap/alignment, ground, arcing to metal before the tip, clean with sandpaper or replace.
4. Igniter OK but burners do not light check gas supply and manifold pressure (verify gas valve inlet and outlet pressure), orifices for restriction, gas valve manual switch ON, 24 V on the IFC gas valve pins and wiring/continuity to the valve.
5. On 90+ furnaces check the auxiliary limit is closed and, on upflow models, that the drain pressure switch is closed - clear a blocked drain, or replace the switch if the drain is clear.
6. Burners light then drop out confirm L1 and Neutral are not swapped at the IFC and junction box, check IFC and unit ground, clean the flame sense rod (sandpaper) and check its wire to the IFC.
7. Check that flame carries across all burners and all burners stay lit.
8. Only replace the IFC after all of the above - most failures are not the control.

Settings for these units

• Filter sizes (Table 12) · Rheem 90RJ/90TJ 90 Plus
• Minimum clearance to combustibles · Rheem 90RJ/90TJ 90 Plus
• Filter sizes (Table 9) · Rheem (-)GRC/(-)GTC 90 Plus
• Minimum clearance to combustibles · Rheem (-)GRC/(-)GTC 90 Plus