Error Code Code 24

Carrier 58MVP Error Code Code 24: Secondary Voltage Fuse Is Open

TL;DR
Indicates the secondary voltage (24V) fuse is open. There is a short circuit in the secondary voltage wiring. This can be an intermittent problem. Check outdoor unit contactor — failure to pull in can cause excessive current draw on the low-voltage circuit.
Disclaimer
This article is for informational purposes only and does not guarantee the accuracy or completeness of the information provided. Always turn off power and gas supply before attempting any repairs. If you smell gas, leave immediately and call your gas company. Consult a licensed HVAC technician for diagnosis and repair. Any actions taken based on this information are at your own risk.

What Does Code Code 24 Mean?

Indicates the secondary voltage (24V) fuse is open. There is a short circuit in the secondary voltage wiring. This can be an intermittent problem. Check outdoor unit contactor — failure to pull in can cause excessive current draw on the low-voltage circuit.

Common Causes

Cause Likelihood DIY?
Short circuit in secondary voltage (24V) wiring Most common ✗ Call a pro →
Short in thermostat wiring Common ✗ Call a pro →
Defective outdoor unit contactor causing excessive current draw Common ✗ Call a pro →
Short circuit in limit switch circuit Uncommon ✗ Call a pro →
Short in pressure switch wiring Uncommon ✗ Call a pro →

When to Call a Professional

Contact a licensed HVAC technician if:

Sources

  1. Carrier 58MVP Service and Maintenance Manual, p.11 – LED Codes
  2. Carrier 58MVP Troubleshooting Guide, p.19–20 – Fault Code 24