LED1 OFF / LED2 OFF No power to the control

What the control is telling you

Neither LED lights. The board is not getting 120 V, or the 24 V side is dead.

Applies to: G43UF-24B-045 through G43UF-60D-135 (SureLight boards 32M88, 78M47, 100973-01)

Likely causes

• No 120 V at the furnace
• Furnace or make-up box miswired
• Blown fuse on the board
• Door interlock switch not made or failed
• Transformer failed
• Control board failed

Test and repair steps

1. Turn off power at the disconnect before touching wiring or components.
2. Check for 120 V at the furnace and trace the cause of any power loss.
3. Check the wiring from the make-up box to the transformer and the 24 V wiring to the board.
4. Check the fuse. If it keeps blowing, look for a short.
5. Make sure the blower door is on and the door switch closes. Check the switch for continuity when pressed.
6. Check transformer output for 24 V.
7. If everything above is good, replace the control board.

Settings for these units

• Recommended filter size by cabinet width · EL296UHV
• Recommended filter size by cabinet width · Lennox SL280UHV
• Filter sizes by cabinet width · Lennox ML180UHE
• Filter sizes (filter rack kits) · Lennox EL195UHNE
• Filter sizes by cabinet width · Lennox SL297NV

Models that show this code

10 models in Lennox G43UF

Other codes on the same units

• LED1 & LED2 alternating SLOW flash Watchguard lockout - burners failed to ignite or repeated failures
• LED1 & LED2 simultaneous FAST flash Normal - heat call in progress
• LED1 & LED2 simultaneous SLOW flash Normal - power on, idle, cooling or continuous fan
• LED1 FAST flash / LED2 SLOW flash 120 V line and neutral reversed
• LED1 OFF / LED2 ON Control board failure or control wired incorrectly
• LED1 OFF / LED2 SLOW flash Prove switch (pressure switch) open
• LED1 ON / LED2 OFF Control board failure or control wired incorrectly
• LED1 ON / LED2 ON Control board failure or control wired incorrectly