If you have access to an electric welder you can get a cheap box end
wrench, pound it over the plug, and weld it right on. I did that a while
back when I had a Vanagon here with the same problem. I think the heat
from the welding helped too as it turned easily after I welded the
wrench to it.

Mark

Chris Renz wrote:

> that sounds about right. I think over the years using the 12 point 13mm
> slowly rounded it off to where it is now.
>
> either that or I have stripped the threads and just don't know it yet.
>
> I tried the 1/2" because it actually fits right on there already, but its
> doing the same thing.
> When its light out again ill try it once more and make certain it's as
> tight
> as can be up against the plug.