laguna rear demister

guys am after some advice and help please. my rear demister seems to not want to demist the rear window. on most cars when the demister is on you can see the tell tale lines appear across the rear screen....on mine you don't :(

now at the front when i press the button for the demister

the button lights up
i hear a click coming from some where behind the fuse box

at the rear i have checked the continuity and there is a complete circuit
if i run a lamp tester over the heater elements they light up too so no broken traces.
the block in the boot i have left that connected BUT i have also spliced into the wire that leads into and out of the block to form a direct link, for the demister

still it refuses to demist or it is the slowest weakest demister ever made.

anyone any other ideas of what i can check

many thanks

forgot to add its an S reg 16v 1.6 petrol other than the above annoyance it goes fine

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