CTC Intermittent Flame Sensing / Control Relay Chatter

Furnace cycles on and off rapidly with clicking from the control board but burners do not stay lit.

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

Loose control board connections, Weak flame sensor, Unstable 24 V supply, Failing control board relays

Safety first: Turn off power before reseating connectors.

Steps:

Inspect and reseat all low-voltage and high-voltage connectors on the CTC control board.
Clean or replace the flame sensor as described in earlier steps.
Check the 24 V transformer output for stability; replace if voltage is low or fluctuating.
If relay chatter continues, the control board may be failing and should be replaced by a technician.

Hard 4/5

CTC Integrated Furnace Control Board

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