Carrier Furnace LED Off
WarningShown as: Status LED is completely dark - no flashing at all
The control board has no power. The manual's first step is to verify 115 VAC is reaching the board at L1 and L2 and that the transformer is delivering 24 VAC at SEC-1 and SEC-2.
Manual wording: “CONTINUOUS OFF - Check for 115VAC at L1 & L2, & 24VAC at SEC-1 & SEC-2.”
Documented for: 58MCB, 58MVP, 58UVB and most Carrier 58-series furnaces
Likely causes, most common first
- No 115 VAC at the furnace (breaker off, service switch off)
- Blower access door not seated, so the door interlock switch is holding power off
- Blown transformer or open 24 VAC circuit
What you can safely check yourself
- Make sure the furnace blower door is fully closed and latched - the door switch cuts all power when it is open
- Check that the furnace service switch (looks like a light switch near the furnace) is ON
- Check the breaker labeled furnace in your electrical panel
When to call a technician
If the door is seated and the breaker and service switch are on but the board is still dark, the transformer, door switch, or board itself needs a technician with a meter.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- 58MCB 4-Way Multipoise Fixed-Capacity Condensing Gas Furnace - Service Manual (Carrier, 58MCB single-stage condensing gas furnace) · checked 2026-08-25
- Troubleshooting Guide - Variable Speed, Two-Stage Gas Furnaces (Form 58-06T) (Carrier, 58MVP, 58UVB and other Carrier variable-speed two-stage gas furnaces (replaces 58MVP-10SM)) · checked 2026-08-25