Non-Working Rear Window Defogger in Crewmax

With the freezing temps around here (Montana) I've noticed that the heat lines in my power rear window of my Crewmax do not defrost/defog the window. When I engage the deicer/defogger button on the center console, the side mirrors clear up just fine tho.

Can anyone point me in the right direction for how to diagnose this problem? For example, is there a fuse or relay/switch that I could check to see if it needs replacing. Or is it something that should be repaired by someone who knows what theyre doing?

Thanks!

 

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Have you tried looking to see if there is a fuse or relay for the rear window defrost?

 

No, but that was just my first guess as to why it stopped working. FWIW, I purchased a year ago and don't think it's worked since owning it. Would the owners manual explain all of the relays and fuses so I'd know which one(s) to check?

 

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Have you tried reading the owners manual to see if it explains all the relays and fuses so you'd know which one(s) to check?

 

Just went through the owners manual. There is not diagram or other explanation for what each fuse corresponds to. Guess I'll poke through the fuse box and make sure theyre all intact.

 

When you pull off the cover, on the underside of the lid, there is a diagram of each fuse/relay (numbered) and a list of what each fuse/relay controls.

 

It might not be the fuse. Often, the metal plate that attaches the wire to the defrost grid comes loose from the window. Or the grid itself deteriorates or detaches. I think it’s more likely to happen in extreme temperature and humidity swings such as you’re experiencing.

Permatex, Easton, Loctite, etc all make kits you can buy on Amazon. You may need to remove your rear seat and take off the rear cab panel to get to where you can see the part of the window where that metal tab attaches. You may need to buy a new generic metal tab. Or you may just need the small amount of conductive adhesive in one of these kits to get it to start working again. It’s a simple fix, but you have to follow the instructions exactly.

The other problem might be a break in the grid lines. There’s a repair kit for that as well. Check out these Amazon search results, and good luck!

 

I don't know if you have manual or automatic climate control, but if you have the auto A/C, the mirror and rear window defrost/defog switches are separate. They are all on one switch on the manual system.

 

Found the corresponding defog relay in the engine bay. Tested it and appears to be in working order. I'll think more about examining the metal plate and the window lines.

 

Update- the rear window ground was broken off the glass. Not the easiest fix since I had to remove the back seats to get access....