Heater makes clicking noise when blower shuts off

Thanks for all the input. Will check the items listed and post the results.

Old-Biscuit wrote:
Sounds like igniter is firing.......which means DC is still going to circuit board when it should not be there.
Turning local ON/OFF---CB OFF drops the DC out.

Only way DC can get to Circuit Board is via Sail Switch and limit switch circuit.
Limit switch is always closed (unless high temp)
Sail switch should only close when fan runs and open when fan stops.

Stuck sail switch.

It is right by that on/off--cb
Small micro switch with a 'paddle' that still into fan blower chamber
Next time you hear the clicking...check if paddle is still 'up' (switch closed)
Move paddle down (switch open) should stop clicking noise
IF so........then replace sail switch (can try cleaning)

X2, Sail Switches cause numerous "failures" in several circuits. The common problem is just as the op stated, "clicking".

Make and model of furnace?
It could be the time delay relay. Some are mounted on the circuit board and others are not.
It could also be a bad thermostat. Make and model?

Could it be some moisture on the circuit board? I had a similar problem with my heater and it was moisture. You might want to try using a hair dyer on the board to see if that's the problem.

Sounds like igniter is firing.......which means DC is still going to circuit board when it should not be there.
Turning local ON/OFF---CB OFF drops the DC out.

Only way DC can get to Circuit Board is via Sail Switch and limit switch circuit.
Limit switch is always closed (unless high temp)
Sail switch should only close when fan runs and open when fan stops.

Stuck sail switch.

It is right by that on/off--cb
Small micro switch with a 'paddle' that still into fan blower chamber
Next time you hear the clicking...check if paddle is still 'up' (switch closed)
Move paddle down (switch open) should stop clicking noise
IF so........then replace sail switch (can try cleaning)

Barnaclebills wrote:
Our heater works just fine. However when it shuts down and the blower turns off it will start clicking. If I remove the metal cover there is a on off rocker that sits next to a circuit breaker. If I turn this switch off then back on the click goes away until the furnace runs and shuts off again. Heater worka fine otherwise. It is a attwood heater. Unit is a 2002 and looks original. Thanks for any input.

sounds like you have a circuit control board problem and a relay is exciting and shutting off in rapid succession or the electronic igniter is shorting out or coming on when its not supposed to so again bad control board

Any chance it could be a piece of debris that flops down when the blower is winding down and the air flow drops off?