24
Moderate
Carrier · Central Air Conditioners & Furnaces
Secondary Voltage Fuse Blown
Quick Answer
Error code 24 on your Carrier Central Air Conditioners & Furnaces means: Secondary Voltage Fuse Blown. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
Likely Causes
How to Fix It
1
Locate and check the 3-amp or 5-amp fuse on the control board
2
Disconnect all thermostat wires and check for shorts between conductors
3
Check transformer output voltage (should be 24-28VAC with no load)
4
Inspect outdoor unit contactor coil for short circuit
5
Reconnect wires one at a time to isolate the shorted circuit
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Parts You May Need
Automotive-style 3A or 5A fuse
24V transformer
Thermostat wire
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