On Sat, 14 Jul 2007 06:14:24 -0700, wrote:

On Jul 14, 1:00 am, "Mike Dobony" wrote:
"mm" wrote in message

...



On Fri, 13 Jul 2007 20:24:43 -0500, "Mike Dobony"
wrote:

"Bobo" wrote in message
. ..
On Fri, 13 Jul 2007 23:38:13 GMT, "Mike Dobony"
wrote:

"Telstra" wrote in message
...

"Bobo" wrote in message
om...
What's up with a third horse whole house fan motor that has begun to
occasionally run backwards. This started happening about the same
time
the switch went bad. I put in an identical switch and didn't mess
with
the motor wiring. It's AC, 120.
Thanks

The Fan motor capacitor has two terminals each terminal connected
to a motor winding and one also connected to the Active. Switching
the Active to the other terminal will reverse the rotation of the
motor

But how can this happen occasionally?

Googling I've found one reference to a motor running backwards
sometimes as the capacitor failed, I haven't found even one more
mention of this though,

That is a possibility, but the explanation given the circumstances does
not
fit. Switching the active to the other terminal will reverse rotation
permanently, not occasionally.

But he's stopped talking about switching the actived to the other
terminal.

Okay, poorly worded question. How would a switched connection cause
occasional reversal? Is that better?

His words just above yours are "as a capacitor failed".

That might be intermittent.

Thought. Let's say the start cap is intermittent or failed and there
is a thermal draft rotating the blades. Applying power...the motor
will continue in that direction.

You might have it there. I was surprised how much wind was blowing in
the attic when I crawled up there to look at the thing. It sits right
under a ridge vent. I got it to run the right way by starting the fan
in the right direction with a stick and then turning it on.