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Fuse box rear , fuse #23 30 amp ! Do you know where this is located ? There is also a relay for the Rear window defogger , located in the same rear fuse box .
Fuse Block - Rear
Left side of the luggage compartment, behind the left rear wheel well . But you really need to know how it works , you can check fuse an relay .
Rear Window Defogger Operation
Battery positive voltage is supplied through the BATT 1 fuse in the underhood fuse block to the rear defog relay switched input. When the rear defog switch button is pressed, the body control module (BCM) energizes the rear defog relay by providing a B+ to the control circuit of the rear defog relay. This allows battery positive voltage from the relay switched input through the switch contacts and out the relay switched output to the rear window defogger grid. The HVAC control module houses the rear defog switch and also illuminates the rear defog indicator on the switch button, upon this request. Ground for the rear window defogger grid is provided by G301 for the Sedan or G302 For the Extended Sedan.
I found this. Your heated mirror also works off that relay. You can do ohms test on the grid, if the grid is open, no continuity. The auto store should sell a product to paint over the open spot to restore continuity, if you can find the open spot.
Not trying to cause trouble, just killing time. Have a good day.
Did you check voltage and ground at rear defog connector, purple wire should be voltage, black wire is ground. Check to see what your missing, defog turned on. If you have good voltage and ground, then suspect a break in the defog grid. If you can locate the break, the auto store should have some stuff you can paint over the break to allow continuity for the grid.
Also, you should be able to check grid continuity, ohms test. If no continuity, something wrong with grid.
Here is partial diagram.
First check all fuses, second check for 12v power at the connector to th rear window, a test light or volt meter on dc voltage,if there is power use an ohm meter to check the window grid with the power connector disconnected.if open the connection is either open or bad. if there was no power at the connector check the power from switch all the way back to the window
Couple of things to check - first look for any scratches through lines, a couple of scratches will not let power run from side to side. The other is -> with a test light or voltage meter -> put (+)cable of meter/light to small electrical connector that attached to your window and (-) cable to a good ground (metal) light will come on/meter should read voltage there.
Check for good wiring to the grid.Take the two wires off of the grid and use one end to a load[such as an old headlight bulb or what ever you can find that pulls around 5-10 amps].A test light can be used but it draws no wheres near as much power as the grid does but it will get you started.Put a test lead from each of the grid wires to your load source or test light to see if it works or lights.If the load is dim or turning slow[if all you found was a fan motor or something like that] then you need to find out if it's a bad ground or a corroded power wire.Put the load from the power side to a good ground elsewhere on the vehicle and if it works normally then you have a bad ground.If it still doesnt work like it should then you need to trace the power circuit wiring.This is not brand specific it's just general electrical trouble shooting advise so i hope it help[s you out,a volt meter will show you voltage even if only one strand of wire is still connected so this should be doe when ever electrical problems appear to be normal but still don't work.
Yes there is a relay, but it is part of the hvac control head. There are two fuses in the system one is labled the hvac fuse it's a 10amp and there is a RR defog 30amp fuse. Those supply power to the hvac control head. Control head supplys power to the rear defroster. There should be a purple wire in c3 terminal D on the back of the control head. See if that has power when you turn on the switch. If it dose not then there is not power out put to the rear defroster. If so then the problem lies further down the line.