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Broan QS2 range hood fan control...


G. Paul Ziemba

Can anyone explain the electrical principles of the Broan \"Quiet Series\"
(also called \"Allure\") range hood fan?

This unit was made in 2005. There is an electronic control board
with three relays that appear to activate three blower speeds
(low, medium, high). The blower motor has four wires and there is
a 7.5 uF capacitor involved.

There are pushbuttons for the three speeds. Speeds 1 and 3 work correctly.
After 14 years of use, speed 2 (most frequently used speed) worked only
intermittently but did respond to impact adjustment. Now it doesn\'t even
do that.

I can hear a relay click for each of the three speeds. but the motor
does not turn at all for speed 2. I suspect either failed relay contacts
or a bad joint/broken trace, but I haven\'t gotten a look at the circuit
board yet (pending arrival of new membrane button cover which gets
destroyed when accessing control board).

Anyone know how the motor circuit works? Given that there are only
four wires it seems to be a bit more complex than common-cap-1-2-3.

Oh, and although it would be easy to throw parts at it, the control
board retails for $200. I\'d be happer to see if I can resolder or
throw a $5 relay at it.

G. Paul Ziemba
FreeBSD unix:
10:11AM up 50 days, 17:52, 41 users, load averages: 0.16, 0.18, 0.22


Three windings on the motor and a common. Most typically, such things are one/two/both, but in your case, it is one/two/three. So:

a) determine the motor voltage - likely the same as the line voltage.
b) If you can remove the motor from the circuit, do so.
c) Determine the common.
d) Apply voltage at each winding - additionally, not sequentially - and note if the motor speed increases as expected.
f) If so, the relay is likely bad. 15 years is not a bad service life.
g) If not, the motor likely bad - and it will be a close-run thing whether to replace the hood or just the motor.

Best of luck.

Peter Wieck
Melrose Park, PA
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