Coleman-Mach Er fault code — Thermostat
Applies to: 9330-33 multiple-zone thermostat
What Er means
The Coleman-Mach 9330-33 manual says Er displays when ambient temperature is outside the thermostat display range or when a remote temperature sensor has a problem.
Owner-safe checks
- Compare the thermostat display with room conditions.
- Record the affected zone and whether Er appears continuously.
- Avoid changing wiring or internal thermostat settings.
Service-only work
- Remote temperature sensor circuit, zone control board, signal wiring, and rooftop HVAC service should be performed by trained technicians.
Safety boundary
Disconnect power before thermostat or HVAC service. Do not open rooftop electrical compartments unless qualified.