Furnace displays E20, often immediately after power-up or reset.

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

Repeated ignition failures, Overheat events, Internal self-check failure, Control board safety circuit fault

Safety: Do not repeatedly reset a furnace that immediately returns to lockout; this can be dangerous.

Note previous behavior: Consider what happened before E20 appeared (e.g., noises, smells, previous error codes). This information will help a technician.
Power cycle once: Turn off power for 60 seconds, then restore and attempt a single reset.
Do not bypass safety devices: If E20 returns, do not attempt to bridge thermostats or sensors. This must be investigated by a qualified Chaffoteaux technician.

Professional Required 5/5

Main Control Board (PCB)

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