Bone headed move with the Thermostat Knob

[Murray01]

This morning I got up and decided to light a small fire in my Princess 32 manufactured in 2025. The thermostat knob was at the 6:00 position, me not thinking I turned it past the 6:00 o’clock position to about the 9:00 o’clock position.

It appears that the shaft DIDN’T turn but the control knob did.

What I have now is: 9:00 is now wide open air intake(should be 6:00)
9:00-6:00 the shaft to the thermostat doesn’t rotate while the knob does
6:00-2:00 works normal, shaft turns with the knob however I can now turn the knob and shaft to the 1:00 position.
The above is starting from wide open air to minimum air.

Now working backwards, from minimum air(1:00 to 9:00) to maximum air.
1:00-4:00 shaft doesn’t turn with the control knob
4:00-9:00 shaft turns and fire picks up

What I’m thinking of doing is turn the knob to the 9:00 o’clock position, wide open air, loosen the set screw on the control knob and set the control knob back to the 6:00 o’clock position. I can hear the thermostat flapper closing at about the 2:00 o’clock position and the fire dies down as it should. I have not taken the cover off the back, the cover I’m referring to is “No user serviceable parts inside. Do not remove this cover”

Any suggestions to fix this “dead spot” would be welcomed.

 

[Dieselhead]

Your plan is what BK recommends when the knob goes out of calibration.

 

[Murray01]

All I can find in the owners manual.

THERMOSTAT or THERMOMETER MAINTENANCE Any thermostat or thermometer maintenance must be completed by a certifi ed installer. If the thermostat or thermometer malfunctions, contact your dealer for replacement

Was wondering if there was a slot/flat spot on the shaft where the set screw should sit or is just friction of the set screw keeping the knob and shaft aligned as it came off the assembly line? Anything else I should know before I fix what should be a straight forward readjustment?

 

[Dieselhead]

No flat spot that I’m aware of. The blurb in the manual about thermostat adjustment refers to what’s behind the cover on the back of the stove, you never want to adjust anything in there. Just adjusting the knob on the shaft is almost a maintenance item after time on these stoves.

A snip from the VP:

 

[Murray01]

Thank you.

Surprisingly this is the first time I’ve had an issue with either of the 2 BK I’ve owned.

 

[Murray01]

Another question regarding the thermostat.

When the stove is cold the thermostat dial is easy to turn. Once the stove is started, thermostat on high, bypass open until the thermometer is in the active zone the thermostat dial gets very stiff and requires a lot of force to start dialing the thermostat knob back. After leaving the stove on high for 20 minutes or so the dial becomes much easier to dial back.

I’m assuming while the stove is coming up to operating temperature something inside the thermostat assembly is expanding to the point where it takes considerable force to dial it back. Our older BK Princess did not do this.

Any suggestions what’s happening and how to rectify this stiff dial?

 

[Highbeam]

Ignore the warning label, my label actually fell off, there are definitely user serviceable things under that back cover. One is to lube the spring washer that provides tension on the operating shaft so the knob goes from turning skritchy and tight to nice and smooth. Also, the throttle blade itself and the shafts get dirty and benefit from clean and lube.

You'll also see the hard stop at max thermostat setting that you'll use to reset the knob position.

 

[Murray01]

Thank you

 

[Murray01]

On the back cover there is 3 screws, two are Robertson, same as my old BK, the third screw is about an inch above the two Robertson. I’d guess US manufactured stoves would have Phillips screws instead of Robertson. This mystery screw had a security head on it. Appears to be a Torx with a post in the middle.

Is there something attached to the mystery screw or is this an anti tamper screw?

 

[Dieselhead]

On the back cover there is 3 screws, two are Robertson, same as my old BK, the third screw is about an inch above the two Robertson. I’d guess US manufactured stoves would have Phillips screws instead of Robertson. This mystery screw had a security head on it. Appears to be a Torx with a post in the middle.

Is there something attached to the mystery screw or is this an anti tamper screw?

View attachment 349710

You don’t want to remove that one as it limits max travel for the thermostat flapper. It just goes through the cover annd nothing else. Also why you make sure tstat is closed before reinstalling cover, or it can wedge above that screw and stove will be stuck at full throttle.

 

[Highbeam]

Yep, just leave the upper screw alone. The first time you remove the cover you might have to fight some black silicone that spooged out from under the thermostat when it was first assembled.

Lots of square drive screws on my princess here in the US, though I do believe it was made in Canadia.