I have an 88 GTA and I am having a little trouble with the rear window defogger..ever since I bought the car it doesn't seem to work properly...when I turn it on the light illuminates and the window will begin to demist but the time that it remains on varies from a few seconds upwards and it never seems to be on long enough to demist the window totally. I'm guessing there's some sort of timed relay or something to stop it being left on too long and maybe this is faulty?? Can anyone let me know what to look for...and where!
Thanks guys!

 

The time delay module is built into the control switch.

Tim

 

check your grounds on the end of the rear window shocks and check if they have some sort of plastic piece that fits between the screw ends.
because if there isn't it can cause the defogger to short and then shut of the defogger.