Rear window defrost not working on drivers side and possibly drivers mirror.

[Snakedoctor]

No, from what I’m seeing on the diagram is that the DDM (drivers door module) get its power from the BCM, than the DDM send signal to the outer mirror. They don’t have any wires in common. Most likely just a coincidence. Is it a tow mirror or a standard mirror? I traded my standard mirrors for tow mirrors and noticed the tow mirrors defrost a lot slower.

I have the tow mirrors. I know the drivers side is supposed to be slower as it is much thicker glass but even the lower convex mirror wasn’t feeling any different at all.

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[jkosh22]

I have the tow mirrors. I know the drivers side is supposed to be slower as it is much thicker glass but even the lower convex mirror wasn’t feeling any different at all.

I’m not 100% sure but I don’t think other convex mirror is heated. I think it’s just the upper portion of the glass.

 

[Aramis76]

One quick question, i keep reading that the tow mirrors only heat the top mirror but you seem to indicate that the lower convex one heats up also?
OEM mirrors or aftermarket?

 

[Snakedoctor]

One quick question, i keep reading that the tow mirrors only heat the top mirror but you seem to indicate that the lower convex one heats up also?
OEM mirrors or aftermarket?

OEM mirrors. Not all tow mirrors will according to google but some do.

 

[Snakedoctor]

Hopefully that’s the issue! But just for reference if anyone needs it. I have a wiring diagram for 2021 Lariat, it’s all the same between trim levels, it appears each window has its own grid working independently of the same power and ground. So you most likely have a driver side fridge failure or a loose connection. It it would most likely be the other panels also. Had rear defrost overheat window in my 2013 f150 and blew out the glass, has to replace entire rear window assembly. Hope this helps! Sorry if the photos look bad, I took them off our shop tablet.

I appreciate all of the info. It appears this usage was not fixed yet. I wish I had access to a thermal camera to see the mirror as well. Since I paid my $100 deductible for the warranty work I’m bringing it back to the dealer.

 

[jkosh22]

No problem. Hopefully the dealer can get it all sorted out!

 

[Snakedoctor]

No problem. Hopefully the dealer can get it all sorted out!

Thanks though I’m losing faith in this dealer. Advisor told me at drop off that it could be a glass issue which isn’t covered under warranty (extended premium care). All my research online says the heater grid is covered just can’t be submitted as new glass, he just pushed it off saying Ford always kicks it back. So time will tell there.


I did get a cheap thermal camera as I could have a few other uses and within seconds you can see there’s no heat to the rear window! After a few moments I saw the little warm spot on the bottom left corner so it gets power just not heating up.

I was also able to see the drivers side mirror does heat up however somehow even after a 20 minute drive with it on barely even cut through the dew where the passenger mirror was completely clear within 5 minutes.

Overall frustrating on a $73,000 marked vehicle with less than 40,000 miles at 3 years old.

 

[jkosh22]

I’m sorry to hear they are giving you the run around. It’s expensive to fix either way too which really sucks. That thermal camera will come in handy more ways than you think! But I agree. My heated steering wheel quit working on my lariat. I bought it used a year ago, it’s still frustrating cause it costed 70k 4 years ago.

 

[Snakedoctor]

I’m sorry to hear they are giving you the run around. It’s expensive to fix either way too which really sucks. That thermal camera will come in handy more ways than you think! But I agree. My heated steering wheel quit working on my lariat. I bought it used a year ago, it’s still frustrating cause it costed 70k 4 years ago.

Thankfully there’s several dealers I’d be willing to travel to if necessary. This particular one I just use for convenience and it’s where I bought from.

For your heated wheel, is the wheel itself? Or something else?

 

[jkosh22]

Thankfully there’s several dealers I’d be willing to travel to if necessary. This particular one I just use for convenience and it’s where I bought from.

For your heated wheel, is the wheel itself? Or something else?

At least you have options!

Yeah I think it’s my steering wheel, I have a scanner at work and was watching live data and the temp for the wheel was pegged at -40 which for thermistors means it shorted. So it’s most likely the steering wheel. It seems to be always something!

 

[Snakedoctor]

At least you have options!

Yeah I think it’s my steering wheel, I have a scanner at work and was watching live data and the temp for the wheel was pegged at -40 which for thermistors means it shorted. So it’s most likely the steering wheel. It seems to be always something!

Interesting, I’m curious if my window issue is bad wiring or heat. Do you know what part actually makes the heat? Is it an element in the glass itself? Since it shows as a small hot spot it makes me wonder.

I also have a lariat steering wheel in the garage if you might in interested in trying a whole different wheel we can arrange something I’m sure.

 

[jkosh22]

The lines you see on the window are part of the grid which is electronically charged when defrost is turned on. It heats up with electricity. So you most likely have a short in the grid (wire) in the window.

Thanks for the offer! I’m going to focus on the kids and family this Christmas and not indulge in myself. Especially as something as small as a heated steering wheel. As annoying as it is.

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