It doesn't seem likely that the tree would be getting "too much" light and one wouldn't expect the wooden wall to reflect that much in the way of heat (compared with a brick wall). I'm comparing with my one tree which is in a very exposed west facing position. But if you think this is the problem, have you the option of painting a different colour (no, I wouldn't either) or perhaps fixing a piece of lattice to the wall which would cut down the degree of reflection.

Looking at other reasons, it sounds a bit like the tree is not getting enough moisture and being close to a building, this might be the problem. Walls & buildings can have a huge impact on the amount of rain which falls near them and we don't tend to water too much close to a building. Can you dig a deepish hole a metre or so out from the tree on the building side and see what the moisture content really looks like.

Another reason could be something in the soil which the pear doesn't like. Possibilities might be too much lime (if you have brick/concrete foundations which are fairly new) or even something that may have been applied to the soil to deter white ants.