Whitfield Quest pellet stove fan motor relay buzzes when switched to high speed.

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SaddleBear

New Member
Jan 14, 2021
4
Colorado
I have a Whitfield Quest pellet stove. The two speed fan motor causes a 60hz buzzing noise in the control board's relay when it's switched to high speed. It works fine on low speed. High speed also works, it's just that the relay buzzes loudly. I replaced the relays on the control board but that didn't fix it. I need to figure out if the issue is with the high speed circuit on the blower motor or in the control board. My hunch is it's the high speed circuit on the motor. We always ran the motor on high it was never run on low. The control board is $300 and the motor is $100. Any ideas which I should replace first or a way to diagnose this? Anyone experience this problem?
 
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SaddleBear

New Member
Jan 14, 2021
4
Colorado
Thank you for the reply.
There are 3 wires to the fan motor: red, black, white.
When the motor is unplugged, the relay on the control board still buzzes when switched to high speed. So that sounds like a control board issue to me, however, just in case:

The voltage between black & white on low is 20 volts and on high, 115 volts.
The voltage between red & white on low is 20 volts and on high it's still 20 volts.
 

Ssyko

Minister of Fire
Nov 6, 2017
4,204
Lorraine NY
Yeah there’s something gone haywire on that board. 20v is definitely not enough to run the motor. The motor is probably a center tap in the windings for low and uses the end tap for high. You could test them with a lamp cord plugged into the wall
 

Stovensen

Minister of Fire
Feb 1, 2010
540
Denmark, EU
Hello SaddleBear, and welcome to the forum,
The electric control of the convection blower on your regular Quest is quite different from my Quest Plus stove, and most other Whitfield stoves, which use triacs to control the speed.
The convection blower motor on your regular Quest has two separate windings, a high speed winding and a low speed winding. The relay on the control board simply toggles between these two windings. On the high speed setting, the full main voltage ( 115 Vac ) should be present at this winding and vice versa on the low speed winding at the low setting.
The buzzing sound from the relay indicates that someting is wrong on the control board. The original relay was a Zettler AZ941 CT-48DE
Are you absolutely sure that you found the correct replacement? The number 48 indicates that the nominal dc voltage to energize the relay should be 48Vdc. And according to the datasheet it "must operate" at 38.4 Vdc.
The circuitry generating the correct toggle-function could also be faulty, of course.
Let's have a look at the wire colors in a regular Quest. Don't you have these three colors: green, black, white on the wires to the motor:
Quest wiring diagram.jpg
BTW, good job in replacing the relay. Not easy at all to unsolder a five pin component on a double sided circuit board.
 
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SaddleBear

New Member
Jan 14, 2021
4
Colorado
Thank you for the response!

I did replace the relay with the exact same one down to the activation voltage. Agree'd, it wasn't easy re-soldering it but I got it done.
You're correct the wires from the control board are black, white(x2) and green. The pigtail to the motor is red, white, black.
I re-checked the voltages. 122V on the green/white pair when on low speed and 108V on the black/white pair. According to your diagram (thank you for that) the voltage is low on the high-speed pair (black/white) probably because of the oscillation in the relay. I was using a Fluke digital meter to test the voltages.

So it's gotta be the control board.... right?
 

heat seeker

Minister of Fire
Feb 25, 2011
3,214
Northern CT
If that is a DC relay, perhaps it's being fed AC due to something shorted on the board. Just throwing that out there...
 

SaddleBear

New Member
Jan 14, 2021
4
Colorado
I'm not skilled enough to do component level board repairs. The relay was obvious but if it's a blown cap or resistor I wouldn't be able to find it. I did remove and re-install the board and it looked in good shape and nothing was shorting.

I am wondering if it's just the high/low switch and it needs to be sprayed out....?

Thinking about it, it's probably a bad cap in the latch circuit that keeps the high-speed relay active.
 
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Stovensen

Minister of Fire
Feb 1, 2010
540
Denmark, EU
Let's think positive, your Quest stove works perfectly on the low setting on the room blower. So you have heat!
On the high setting room blowers are usually too noisy anyway.
Maybe it's worth considering a new hobby in DIY electronics? I can really recommend it. You certainly must have some soldering skills, since you have managed to replace the relay. And you have a Fluke high quality multimeter.
If this is not the case, I know of a repair service that often has been recommended here in this forum:
The cost of a repair should only be a fraction of the price of a new control board.

Good luck in whatever you decide. Let us know how it works out.