CARRIER DIAGNOSTIC REFERENCE STATUS LED — SHORT + LONG FLASH CODES DOC CARRIER-24

Carrier furnace: Code 24 — Secondary Voltage Fuse Open

Q: What does code 24 mean on a Carrier furnace?

Code 24 — Secondary Voltage Fuse Open. A short in the 24VAC wiring blew the board's automotive-type 3-amp fuse. Official: replace with a 3-amp fuse ONLY.

YOUR LIGHT: 2 SHORT + 4 LONG FLASHES — MATCH IT ABOVE

Try DIY first, then call a pro

What does code 24 mean on a Carrier furnace? A short in the 24VAC wiring blew the board's automotive-type 3-amp fuse. Official: replace with a 3-amp fuse ONLY.

GOOD NEWS: THE FIRST CHECKS ARE FREE AND TAKE MINUTES.

Try these first — in this order

Find and fix the bare wire, then a fresh ATC-3 fuse — 5 minutes.

1Check: Shorted thermostat/low-voltage wiring (often nicked during install work)

Still showing the code? See every cause ↓ Get repair quotes near you

Fuse blows again = live short hunting. DIY part cost: $2–5 — a pro visit for this class of fault typically runs $150–350.

What causes it (in order of likelihood)

Shorted thermostat/low-voltage wiring (often nicked during install work) DIY-CHECKABLE

Parts referenced by this code

ATC-3 — 3-Amp Automotive Fuse (ATC-3)

$2–5

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Always match parts against your model's parts list — part numbers vary within a series.

Applies to

58STA · 58STX · Bryant 310/311/312 系 · Payne PG8M 系

Different Carrier generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.

Verified against Carrier 58STA/58STX Installation & Service Instructions (1106202L), p.37 — “use ONLY a 3-amp fuse... status code 24 when fuse needs to be replaced”

Last verified 2026-07-06 · how we verify