Volvo: Rear Defogger, rear defogger, continuity

Question
I recently purchased my 1st 240 (1991) and the rear defogger does not work.  The defog switch lights up, the fuse appears to be fine and I've tested the elements for continuity so I am not sure what is causing the problem.  Could it be a relay issue?

I would appreciate any thoughts that you have on this item.

Answer
I would check where the contacts actually mate with the window.  There should be one on either side of the window.  Sometimes they get corroded or gunked up and can short.  If they are clean, and you can test positively for continuity across the window element itself, it sounds like your relay is bad.  I can't remember where the relay is located in the 91 model, but it is probably buried under the dash.  I would trace back from the button and test the relay when you find it.  They have a history of going bad.  Good luck!