Not sure about the '76, but the rear window defogger switch on my 1970 Coupe is located at about seat level on the left side of the center console (tunnel) cover. It is about 6" to 7" off the floor and just under the dashboard.
In most cases controlled by rear window defogger switch
In most cases controlled by rear window defogger switch
The fuse for the rear defogger is located behind the glove box. Just had mine replaced.
How do I replace the power window switch on 1977 Corvette coupe
It's the driver's window defogger
The heated mirrors on my 1999 Subaru Forester are controlled by the rear window defogger switch which is located in the dashboard console above the heater controls and to the right of the hazard flasher switch. I'm not sure whether the heated mirrors were optional on the early Foresters or not. Anyway, the heated mirrors (and the rear window defogger) will stay on for about 15 minutes when you press the switch. You can turn them off before then if everything has defogged already. Also, the switch only works with the ignition on.
that's the rear window defroster. up is hi, down is low, middle off.
There is a switch on the dashboard to turn on the rear window defroster (also called a rear window defogger in areas that don't have frost). If you cannot locate the switch, take the vehicle to a local dealer of that product, and someone will be happy to show you where the switch is located. If you locate the switch and the defroster will not work, there is likely a blown fuse or faulty wiring, in which case your local dealer will be even happier to repair it for you - for an appropriate fee.
Some rear window defoggers are filaments built into the rear window that heat up when the rear defogger is turned on. This type of window should not be scraped with an ice scraper.
The 1992 Chevy Corvette power window fuse is located in the fuse box. The power window fuse will be in the second column, second from the top.
It is located under the AC and Heat instrument panel
In my case the switch to the defogger was fried and had to be replaced. I would first determine where the problem is, then get a haynes manual and see how hard it might be to fix the problem yourself. If you can't do it then take it to the dealer.