1996 rear window defrost switch

[John Quinn]

Hello all.
I have a '96 V8 Limited AWD. The rear defrost is not functioning. When I press the switch on the dash, there is no "click" and it does not stay depressed like the fog light switch below it.
There's no indicator light when pressed.
I'm assuming this is a momentary switch and fires a relay and timer.
I can't find a blown fuse in the fuse panel and I can test the switch and bulb with a meter.
Does the indicator bulb have to be good for the switch to function?
And if the switch is functional, where would I find the relay?
Thank you in advance.

 

[tinman_72]

You are correct that it is a momentary switch. It turns off on its own after a while.
The bulb does not have to work for the switch to function. I have a '99 that the light does not work but the defrost does.
That is as far as I can help you.

 

[donalds]

The bulb is replaceable just like the instrument cluster bulbs

 

[J_C]

The relay might be in the dash, behind the radio or a bit further right, whether through radio hole or through glovebox hole is easier to get to it?

As far as fuses, which did you check? There is #3 in the under-hood power distribution box, this is a smaller form factor 30A fuse not the big 50A #3 for the ABS. There is also fuse #27 on the interior fuse panel, and there may be another for the GEM itself, though if that one were blown, it seems like other GEM controlled functions would also be inoperable.

The switch bulb does not have to work for the defroster to work, but I would guess it is more likely you aren't getting power to the switch or the switch itself has failed, since that bulb isn't likely to get many hours run time from only being on for the few minutes the defroster is on.

You may need to use a test light or multimeter to check the various points along the circuit to see where power stops (should be above 12V with engine running, around 12V with it off in case a bad connection is causing voltage drop), and make sure the defroster has a good ground as well as the switch. However, the defroster grid failing or having a bad ground, would cause it to not work but not cause the defroster switch to not get 12V, and light up if the bulb and bulb socket contacts are good. Diagram attached below.

Normally I would suspect the GEM itself less than the other components, but a few years back another member found their GEM was bad. Either that or just unplugging and replugging restored an intermittent electrical connector, you might want to unplug, examine contacts, and replug the gem connector.

98 Explorer - no Rear Defrost, GEM failure?

I have a 1998 4WD XLT with the 6 cylinder with about 185K miles. The rear window defroster stopped working out of the blue. There is no light in the switch when depressed. It worked one day and simply stopped working the next. I checked all the GEM fuses and the "Heated Mirror" fuse in the...

www.explorerforum.com

 

[John Quinn]

You are correct that it is a momentary switch. It turns off on its own after a while.
The bulb does not have to work for the switch to function. I have a '99 that the light does not work but the defrost does.
That is as far as I can help you.

Every little bit helps, thank you

 

[Desert_AIP]

My 98 XLT rear window defrost failed three years ago.
The switch worked (verified with a continuity meter), all fuses intact, continuity through the window grid (no electrical breaks), the relay [which is on the right side behind the radio tucked behind the passenger airbag] worked (verified with a multimeter and continuity tester) came down to the GEM module (General Electronics Module).

The GEM provides all the timer functions for the vehicle. Like radio and window power off delay after removing the key, and of course the defrost timer.
The GEM is a 3" x4" black box on the left side behind the radio with 4 wiring harnesses attached to it. I went to the salvage yard and pulled a GEM out of another Explorer, installed it and the rear defrost worked again.

There has to be multiple timers inside because the other GEM functions were operating. I didn't see any burned traces inside the old one, but the swap worked and has worked since 2017.

The switch sends a signal to the GEM not the relay, the GEM timer latches and sends the signal to the relay. When the timer expires it cuts the signal to the relay and the contacts open and turns everything off.

Wiring diagram attached.