DerbyDad03 wrote:
Riddle me this...

I have a fan/light combo unit controlled by a standard toggle wall
switch. The unit is well over 20 years old.

4 position pull chain for fan - high, medium, low, off
4 position pull chain for 4 bulb fixture - 2 on - 2 off, swap the offs
for ons, all 4 on, off.

Here's the problem:

If all four lights are off, the unit makes a single POP when I throw
the wall switch to the off position. The sound comes from the unit,
not the switch.

If any of of the lights are on, I do not hear the POP when I throw the
switch.

The position of the fan chain does not appear to matter. Regardless of
what speed the fan is running at (including off) the POP only occurs
when all four lights are off.

Since there is no current flowing in the light portion of the unit
with the light chain in the off postion, why would it pop when power
is cut off?

It does sound like something is not right in the motor or motor switch
area, probably conductive tracking from 20 years of grime or vaporized
switch contacts accumulating where it can cause trouble.

I'd recon that there may be a little current flowing through the motor
windings even when the motor switch is OFF, and when the wall switch
opens and breaks that current the inductive kick from the stored energy
in the motor windings makes something arc enough to cause the noise the
OP's hearing.

If two or more light bulbs are switched ON they will provide a damping
load across the motor inductance and the "kick" won't reach a high
enough voltage to make the arc occur.

Sounds like it's time for a teardown and inspection. The proximate fault
may just be in the motor speed control switch itself, and not in the motor.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.