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autOMatic Fan sWitch (a.F.s.)
The Automatic Fan Switch must operate correctly for safe operation of the Heatmor
Principle
The fan switch turns the fan on while the outer door is opened to clear the possible excess fuel build up in
the firebox. Along with normal recommended, safe firebox door opening practices, the risk of a flash back is
greatly reduced.
Operation
The Automatic Fan Switch automatically turns on the fan when the front outer door is open. The Automatic
Fan Switch can be over ridden by the Front light and Combustion Air Blower Control Switch and the high limit
will also override the Automatic Fan Switch.
Maintenance/Result
Ensure that the outer door closes properly to activate the Automatic Fan Switch. If the outer door does not
close properly the switch could stay in the “fan on” position or if the Automatic Fan Switch fails in the “fan on”
position, the Heatmor combustion fan will continue to run until the high limit is tripped. Ensure that the Auto-
matic Fan Switch is working properly: if the Heatmor is off when you approach the Heatmor, the fan should
come on when you open the outer door, if it does not, then your Automatic Fan Switch has failed in the
“fan off” position.
Removal/Replacement
1) Turn off the main power supply to the furnace
2) Insert a flathead screwdriver in the top and bottom of the switch and pull out the switch from the corner
3) Carefully (do not touch the bare connections), remove the two electrical wires from the switch
4) Discard the switch and replace with a new switch
5) Reconnect the two electrical connections in the back of the switch
6) Push the switch back into the hole in the corner
7) Turn on the main power supply again
nOte:
If you have been running off your high limit, to determine if the issue is you’re A.F.S. or your aquastat,
you should complete steps #2 and #3 and if your fan shuts off then it was you’re A.F.S .that has failed in the
“fan on” position. If the fan still runs when disconnecting the switch then your aquastat has failed.
