Goodman Furnace: Reversed line polarity
Reversed line polarity on a Goodman furnace: A polarity error means hot and neutral are swapped at the furnace, or the ground isn't good. The board checks it before it'll run, so it stays locked out until it's right. You see it a lot on new installs or after someone changed a plug-in or a receptacle.
Applies to: 34.5 in chassis gas furnaces
Common causes of reversed line polarity
- 115 V AC polarity reversed
- Poor unit ground
- Wiring mistake at the disconnect or junction box
How to fix reversed line polarity: step by step
- Turn power off before service.
- Review the wiring diagram and correct the polarity.
- Verify the ground and correct if needed.
- Check the wiring at the disconnect and junction box and fix anything that's swapped.
- Restore power and confirm the error clears on the next call for heat.
If the unit shows an error code, look it up: Goodman Furnace codes
Source: Goodman GMVC96 Service and Troubleshooting, p. 61. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.