TCS F50F Owner's Manual page 5

When the fan and air cleaner stops, the neon
light goes out. The air cleaner is off until the
heating or air conditioning and fan start again.
M20800
If you don't want the air cleaner to run, set the
On-Off switch to Off to turn off the air cleaner.
Your furnace and air conditioner will operate
normally, but without the added benefit of air
cleaning. Normally, this switch should be on at
all times.
M20801
5 69-1653EF