Carrier status code 24: the secondary voltage fuse is open

What Does Error 24 Mean?

Carrier defines status code 24 as the secondary voltage fuse being open. That fuse protects the 24-volt control circuit, and the guide specifies a 3 amp automotive blade type that must be replaced only with another 3 amp fuse. A fuse opens because something drew more current than the circuit allows, so the fuse is the symptom. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T The fuse rating and the code definition come from Carrier troubleshooting guide 58-3T for deluxe two-stage induced-combustion furnaces. Fuse ratings differ between control platforms, and fitting anything other than the rating in the literature for your exact model removes the protection the circuit was designed around. Owner-safe checks: Establish exactly what has stopped: heating alone, heating and cooling together, or any accessory such as a humidifier. | Check whether the thermostat display is blank or still powered, since that alone tells the technician which side of the circuit lost supply. | Write down any recent work on thermostats, cabling, outdoor equipment, or the building fabric in the weeks beforehand. Qualified technician: Locating a short in the 24-volt circuit, testing the transformer, and replacing the control fuse are tasks inside an enclosure that also carries line voltage, so they belong to a qualified technician. | Never fit a fuse of a higher rating than the literature specifies. The protection the original rating provides is the reason the transformer and board survived the fault.

Other Common Carrier furnace — Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T Error Codes