HVACopediaGoodman · Furnace troubleshooting
Condensate switch open
What is going on
The furnace won't run because the condensate switch is open. The switch trips when water backs up in the drain pan or trap, and the board shuts the furnace down so it doesn't overflow. Check the drain before blaming the switch.
Likely causes
- High water level in the evaporator coil pan
- Plugged trap or drain line
- Drain line kinked or not pitched away from the unit
Check in this order
- Turn power off before service.
- Check the evaporator drain pan, trap and piping.
- Clear any slime or debris and flush the line with water. Make sure it slopes down to the drain.
- Refill the trap if the unit has one.
- Restore power, run it, and confirm water is draining and the switch closes.
Applies to: 34.5 in chassis gas furnaces
More furnace guides
- Airflow lower than demanded, furnace runs on low stage when high stage is expected
- Alternate combustion air opening (upflow or horizontal)
- Alternate vent/flue location (upflow or horizontal left)
- Annual inspection checklist
- Auxiliary limit control (location and purpose)
- Auxiliary limit switch open (blower compartment)
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Source: Goodman GMVC96 Service and Troubleshooting, p. 62. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.