"Roy" no_bother@all wrote in message
...



As it happens I bought a cheapo buried cable detector yesterday and that
does the job.
It detects the film from the inside- not from the outside.
Also tried it on one of the 15 year old units - no response at all.
Nick.

That is right it's supposed to be on the 3rd face from the fornt .. i,e,
inside face of the inner pane.

Rick