Doug Miller wrote:

In article , "CraigT" wrote:
All right, I've been convinced by you guys to open up the wall.

My prediction of what you will find: absolutely nothing wrong.

I still think the cause is what I said the first time: solvent exposure,
either in the form of overspray from staining the deck, or whatever was used
to clean up the overspray.

Before opening up the wall, at least look at the back side of the siding you
removed. If the problem *was* a heat source inside the wall, then the damage
on the back side should be at least as bad as the damage on the face. OTOH, if
there is no (or only slight) discoloration visible on the back side, that
would be the strongest possible indication that the source of the damage was
on the outside of the house -- with solvent exposure being IMO the most likely
culprit.

Very dangerous advice. Heat coming through the sheathing could very
easily build to the level required to soften and deform the vinyl siding
without discoloring the back side. Open the sheathing and see what's
behind. Heck, even cut a 2" hole with a hole saw to look through and
inspect the removed plug.

Pete C.