On May 6, 4:37 am, "Mark" wrote:
They do make a full size 'old work' box that might work. You'd cut a full
size 3 or 4 inch hole thru the siding and sheathing and the box has 'wings'
that spring out inside the wall to hold it in place. I might prefer this to
the thinner pancake box on the surface since it would let you get the wires
back further inside the wall and help prevent water from causing more
corrosion.



Yes that's what I would do; if sufficient depth to put a regular
(circular or 'octagon') box; screwed to something solid or the siding.
Then the new light fixtures would be attached to the box.
Found exactly same thing in the eaves of my daughter's house while
replacing an outside light with one that had proximity sensors etc. No
boxes at all! Wires were wire nutted to the fixture wires; fortunately
nice and dry and no problems, but one heck of a surprise on a house
not that old. Was able to get a box mounted to a piece of 2x4 which
was inserted through the aperture and secured inside with screws.
On my considerably older house I would not ever have mounted a fixture
with 'wood' screws onto the siding as shown by the OP.! The OPs idea
of caulking or a gasket to slow water entry around base of fixture is
a good one IMO.