Goodman GMVM970803BN Error Code E5: Open Fuse
What Does Code E5 Mean?
An E5 code on the Goodman GMVM970803BN means the onboard fuse has blown, cutting off low-voltage power to critical control components. This fuse protects the integrated control module and the 24-volt control circuit from damage caused by electrical shorts. When the fuse blows, the furnace cannot operate at all. If a ComfortNet communicating thermostat is installed, it will display "Battery Power" because it is no longer receiving 24-volt power from the furnace transformer through the fuse circuit.
The most common cause of a blown fuse is a short circuit in the low-voltage (24-volt) wiring. This can occur in the thermostat wiring running between the furnace and the thermostat, in the wiring to an outdoor air conditioning or heat pump unit, or in the connections at the control board itself. Bare wires touching each other or contacting a grounded surface, damaged wire insulation from rodent chewing or rubbing against sharp metal edges, or an incorrectly wired thermostat or accessory can all cause a short that blows the fuse.
A technician must replace the fuse with a 3-amp automotive-type fuse of the correct rating, then systematically identify and repair the short circuit before restoring power. Simply replacing the fuse without finding the short will result in the new fuse blowing immediately. The technician should disconnect thermostat wires and any accessory wiring, then reconnect them one circuit at a time to isolate which circuit contains the short.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Short in low voltage wiring | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Call a technician to diagnose the short circuit in the low-voltage wiring before replacing the fuse — replacing the fuse without repairing the short will cause it to blow immediately
- The technician should inspect all 24-volt wiring including thermostat wires, outdoor unit connections, and accessory wiring for damage or bare conductors, then replace the fuse only after the short is repaired
✓ Verified against manufacturer service manual — March 2026