I have a 2003 Corolla S with a non-functioning rear defroster. It worked last winter (well, for the two months in winter I had it,) and most of the summer it worked to defog the rear window when it was really humid out, but sometimes starting this fall it stopped working.
When I push the button, the light on the button turns on, but nothing happens. It won’t melt snow or remove ice or fogging. I was thinking fuse at first, but now I’m thinking that if the fuse was blown, wouldn’t the little light not go on?
I’d like to do it myself if I can, because lord knows what a repair place would charge me (I mean, even if they’re being honest, I could see it taking an hour or two just to find what’s causing it, and another one to two to fix it.)
If you have a voltage meter, get into the back seat and look for the connector. Usually there’s a little blade connector attached to the window. For one, make sure the connector is snug, but you should also be able to take the connector off and check for voltage with the switch on. If there isn’t any, check the switch and relay. If there is voltage there, look very carefully at the defroster grid-- a scratch across it near the connector can cut the flow of power to the whole thing.
The “gauge” fuse powers the switch, the “defog” fuse powers the defroster. In order of likelihood of failure, the components are fuse, relay, switch, grid. Other than a wiring problem (possible but quite rare), that’s it.
check your manual for the location of the defroster fuse. if the fuse is not blown then put it in and out a few times (to clean the electrical contacts).
if still bad then go to the contacts at the window and wiggle to clean those contacts and make sure they are tight.
if still bad go to the relay for the window defroster and plug and unplug it a few times to clean the electrical contacts.
if still bad check the voltage at the window connectors with a voltmeter/multimeter. if you have voltage then reconnect, if still bad then the grid may be bad.
if you don’t have voltage then check with a ohmmeter/multimeter to see the window connector that goes to the ground has zero resistance to other grounded electrical points (a continuity check). get this connector to the ground to be good.
if you don’t have voltage then the relay may be bad or the wiring to the window has gone bad.
checking the wiring, especially the ground connections can be difficult. you may need to have a person with experience help with the above if you can’t do it.