American Standard Line Voltage Polarity / Ground Fault

Error code 15 and furnace does not start, LED indicates improper line voltage or polarity

Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Hot and neutral reversed at service switch, Open equipment ground, Shared neutral with other loads causing noise, Miswired incoming power to American Standard furnace junction box

How to Fix / Troubleshooting

Danger: Line voltage issues can cause shock or fire. If you are not qualified, contact an electrician.

Verify polarity at disconnect:
- With power off, inspect wiring: black (hot) to switch, white (neutral) to neutral bar, green/bare to ground.
Check ground connection:
- Ensure the furnace cabinet is bonded to the electrical ground.
Have an electrician test:
- Confirm correct 120VAC polarity and grounding at the furnace.
Once corrected, power cycle the furnace to clear the error.

Repair Difficulty

Professional Required 5/5