Windshield fogging up in cold weather

[ctuan13]

I had a similar experience this past Saturday early evening. Two people in the truck and cabin set to 70F on auto. After about three miles of driving it started to fog up and I looked down to see that AC was not on. Turned it on and the situation corrected within a few miles. Truck came out of a 65F heated garage at 31% humidity into around 7F ambient outdoor.

I've had lots of cars. There is not one I can remember for which I did not have to have the AC compressor ON for winter driving. If this truck turns that off without my permission I will be unhappy.

Well in my case, I always have the AC switch turned on, but it was obvious due to the fogging up and confirmed by a scan tool that the compressor wasn't coming on. But yes, in the past, I always left the AC switch on even when running heat, to keep the cabin dehumidified.

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[ctuan13]

I agree with @RickLightning. I'll add that Max Defrost is the best way to clear the windows. It's one button push to turn on, one button push to turn off, and what Ford engineers think is the best configuration to defrost Windows. I trust they've spent more time thinking about it than I have.

Well in that instance, even max defrost didn't seem to clear the fog or activate the compressor. But also, I just find it odd that I've never had this issue before and it's suddenly started happening in identical conditions to previous winters.

 

[data003]

FWIW, my cabin has also been unusually foggy compared to previous winters. I’ve been running the heat uncomfortably hot to compensate but this hasn’t been a problem before. Will try manually turning the AC on, though I shouldn’t have too.

 

[TaxmanHog]

Probably a screwed up strategy in the recent fixes.

 

[Ford Motor Company]

So long story short I'm having an issue I've never had before in my two years of ownership. I pulled out of my heated garage and left my house and like always had my temp set to around 73, vents set to face and floor and the AC switch set to on. I just had a few local errands to run, but after driving about 10 minutes I noticed it felt more humid inside the cabin and I smelled the characteristic smell you get when the compressor cycles off and the condensation on the evaporator begins to evaporate. Within minutes, every window was fogged up so badly I had to pull over because I was driving blind.

I tried every conceivable setting, but the compressor didn't seem to kick on and the fog wouldn't dissipate. Finally I opened the windows to try and eliminate some of the humidity. That combined with max defrost did seem to make some impact, but the entire rest of the drive, there was at least some condensation on the windshield. For reference the Heated garage is ~60°F and outside temp was ~27°F.

When I got home I pulled out my XTool bidirectional scanner and immediately did a full system scan. Other than the expected minor codes for the TCU being disconnected, there were none. I even scanned the ACCM (Air Conditioning Control Module) specifically and all seemed normal, with no faults. When I set the system to Max AC the life data showed the compressor kick on, pull an appropriate amount of amps and soon after the vent Temps began to drop. And yet if I set the system to 73 with the AC switch on, even running for an hour, the compressor didn't kick on once even to periodically dehumidify the cabin. Same with max defrost.

I've never had this happen before and I'm not sure if this is just some sort of Lightning climate control peculiarity or a serious issue. But without any codes and it being difficult to reproduce without the right conditions, I have my doubts that a dealership visit will accomplish much. Any thoughts, experiences or advice?

Hey there! If you need any assistance with this concern, feel free to send us a DM with your VIN and Ford dealer info.

 

[Henry Ford]

Well in that instance, even max defrost didn't seem to clear the fog or activate the compressor. But also, I just find it odd that I've never had this issue before and it's suddenly started happening in identical conditions to previous winters.

Has this happened more than once? Weather is different day-to-day.

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