Furnace shows E18, often associated with condensate pump (if fitted) or external safety devices.

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

Condensate pump failure or float switch activation, External safety thermostat open, Wiring fault on safety loop, Blocked condensate line causing pump overflow

How to Fix / Troubleshooting

Safety: Isolate power. Water and electricity are a hazardous combination; take care around condensate pumps.

User checks:

If a separate condensate pump is installed, check if it is running or making unusual noises.
Ensure the pump discharge pipe is not kinked or blocked.

Technician checks:

Test the condensate pump operation and float switch; replace if faulty.
Verify continuity of the external safety loop wiring.
Clear any blockages in the condensate discharge line.
Reset any external safety thermostats once the cause has been rectified.

Repair Difficulty

Medium 3/5

Required Part

Condensate Pump

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