Carrier furnace code 24: Secondary Voltage Fuse Open
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.
Before you touch anything: the six signs that mean stop troubleshooting and call a pro →
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.
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
Always match parts against your model's parts list — part numbers vary within a series.
Questions about this code
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.
How do I fix Carrier furnace code 24?
Finding the short and replacing the fuse is technician work, since a new fuse can blow again if the short remains.
How much does it cost to fix Carrier furnace code 24?
Cost depends mostly on how long the short takes to find. A visibly nicked thermostat wire may be quick, while a hidden short takes longer.
Applies to
58STA · 58STX
Different Carrier generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Same control platform, same code: Bryant furnace code 24 · Payne furnace code 24
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 · page updated 2026-10-03 · how we verify
Related Carrier furnace codes
These codes use the same status led — short + long flash codes system.