Carrier
No Heat Call Output
Thermostat calls for heat, but furnace does not start; cooling and fan may still work.
Advertisements
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.
Advertisements
Possible Causes
Open W/W1 wire between thermostat and furnace, Failed heat call relay in thermostat, Misconfigured system type (cool-only), Safety lockout on Carrier furnace preventing heat
How to Fix / Troubleshooting
Safety first: Turn off power to the furnace before accessing wiring.
- Step 1 – Verify mode and setpoint: Ensure thermostat is in Heat mode with setpoint above room temperature.
- Step 2 – Inspect W/W1 wiring: At thermostat and furnace control board, ensure W/W1 wire is secure and not broken.
- Step 3 – Bypass thermostat (advanced): With power off, temporarily jumper R to W/W1 at the furnace control board. Restore power; if the furnace starts, the thermostat or its wiring is at fault.
- Step 4 – Check furnace status LEDs: Many Carrier furnaces have diagnostic LEDs. Note any blink codes and refer to the furnace manual.
- When to call a pro: If the furnace does not start even when R and W are jumpered, a technician must diagnose internal furnace faults.
Advertisements
Repair Difficulty
Medium
3/5
Required Part
Carrier Smart Thermostat
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements