Honeywell F300 Operation

Tech Note ©
October 2013
Honeywell Air Flow Switch (AFS)
Air Flow Switch Operation
The air flow switch (AFS) senses differential pressure across its inputs. The AFS signals the air cleaner ON when a vacuum
is present at the unit. Removing the tubing and using a straw to apply a vacuum near the orifice will turn the AFS ON.
Also blowing air into the unconnected input will activate the AFS.
This test will bypass the airflow switch allowing the power supply to operate. If the indicator light does not turn on with
the airflow switch bypassed, then this indicates a problem with the power supply. Note the collector cells should be
removed to insure the output is not being shorted.
Honeywell manufactured two AFS versions. The new version has a smaller circuit board. Zoom in to the photos to
determine your version.
Air Flow Switch Bypass Procedure
1. Bypass the AFS:
• (2012 - Present) Unplug the AFS then connect the two pins marked "bypass AFS" using a jumper wire.
• (Prior - 2012) Short the resistor to ground with a jumper wire, see photo for your model
2. The door interlock switch must be ON
3. Turn ON the On-Off switch
F300 F50 F52 Models ................................................................................................................. 2012 - Present
On the power supply, connect the two pins labeled "Bypass AFS" located on J3 with a jumper. To permanently bypass the
AFS cut the R16 jumper/resistor.
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R16
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J3