mmm somehow I think you are going to have to find someway to disconnect that fan. I would think that it definately would have cooled down the oven faster than usual.
I too find that I would prefer a better set yoghurt, and I don't know whether I am so used to the commercial gelatine set yoghurts, that I have forgotten what real yoghurt sets up like. This is why I have started to drain my yoghurt for 1 hour after setting, for a thicher creamer feel.
I also have another culture on order, and am interested to see whether they give a different thicker set than the culture that I am using now.
Will let you know.