I have a Jotul F600 stove and I noticed lately that once the stove heats up...The Damper lever sometimes get stuck in the middle...It is right in front of the glass doors..All the way to the left is closed and all the way to the right is open...I try to put it around 2 or 3...lately it gets stuck in the middle...The stove is about 10 years old...
The schematic looks familiar to our F400 as far as the primary air slider. There is a cover right inside the door with two screws. This cover allows inspection of the air slide plate. I've had ash and bits of charred wood get in, but not enough to effect the slide. If it does it on the stove heating up, it may be a part slightly warping. I'd start at taking a look under the cover.
I have a Castine (F400) with a similar design. Mine slides smoothly after 11 years. As mentioned above pull the cover off then inspect the slider from there. Hopefully, it's an easy fix.
The stove is cold..no fire going....Slides back and forth with ease...Got me wondering about warping.....
I took a quick look at the slide plate here. As you actuate the lever from high to low, the plate goes side to side as well as back a slight bit. There is a small gap that closes along the back edge of the slide plate when the rod is in the middle. I bet that is where it is hanging up.
