How does cabin heating work?

[WXman]

LOL, same thing, one is >0degC.

Not the same thing at all. One is moisture on the inside of the glass. The other is ice on the outside of the glass. Also, frost happens even above 0C/32F.

What I want to do is simply defog the windshield, which requires dry air. In other words, compressor should be on. Doesn't matter at all which vents the air is coming out of, as long as it's conditioned air.

Now if I get ice on the outside of the glass, then yes I'll use defrost setting. That'll come soon. Getting close to November.

Negative's is that it has the worst "auto" setting I've ever had in 20 years. It's like it's not reading the drivers temp accurately. I need to crank up the temp on cold days and drop the temp on hot days.

This echos my experience as well, but with a 24. My previous ICE F150’s worked great. I could set 70F and leave it there all year.

At least I'm not the only one.


Interestingly, I just looked in my 2025 owners manual and it states:

"When E-Heat is on, an electric heater warms the cabin and keeps the windows from fogging. Turning E-Heat off saves battery power, which extends your driving range. The electric heater is the only source of heat to warm the cabin."

Hmmm.....

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[TaxmanHog]

Not the same thing at all. One is moisture on the inside of the glass. The other is ice on the outside of the glass. Also, frost happens even above 0C/32F.

What I want to do is simply defog the windshield, which requires dry air. In other words, compressor should be on.




At least I'm not the only one.


Interestingly, I just looked in my 2025 owners manual and it states:

"When E-Heat is on, an electric heater warms the cabin and keeps the windows from fogging. Turning E-Heat off saves battery power, which extends your driving range. The electric heater is the only source of heat to warm the cabin."

Hmmm.....

I think the editor(s) in charge of revisions didn't capture the distinctions with the 24+ heat pump functionality.

 

[TaxmanHog]

in the 30 years of F150 ownership, the HVAC system controls have always been problematic, it's a FORD problem, I'm hoping the whizz-bang tesla kids coming to work for Ford have re engineered it for T3

 

[WXman]

I think the editor(s) in charge of revisions didn't capture the distinctions with the 24+ heat pump functionality.

That is very possible but even if I get in the truck and open up the climate settings on the screen it says the same thing.

 

[RickLightning]

No extra noise or vibration. Heat pump works by simply reversing refrigerant flow.

I guess the people that reported both noise and vibration are imaging things?

 

[P-38]

No extra noise or vibration. Heat pump works by simply reversing refrigerant flow.

You must not have heard the fans go to high speed to warm up the refrigerant when it's below 30. It's definitely more noise and a slight vibration from the fans running flat out.

 

[RickLightning]

https://www.f150lightningforum.com/forum/threads/first-night-with-the-heat-pump.23871/

https://www.f150lightningforum.com/...-heat-pump-noise-vibration.22363/#post-447143

https://www.f150lightningforum.com/...heat-pump-comparison-tests.22593/#post-439108

 

[RickLightning]

You must not have heard the fans go to high speed to warm up the refrigerant when it's below 30. It's definitely more noise and a slight vibration from the fans running flat out.

One of the challenges for people living in warm climates is understanding the behavior of features in a cold environment. "Heat pump works great" when you live where winter is 35 degrees may not apply when the temp is -20 degrees.

In Feb, we were in Idaho skiing, and the hotel had no charging. In the morning, the truck battery, after remote starting, was 15.8 degrees. With an 89.5% SOC, and 99.5% SOH, energy was 96.13kWh which works out to 107.4 at 100%. 130kWh at 99.5 SOH yet we were "missing" 23kWh...

 

[El Duderino]

I agree that there is noise I can hear and vibration in the steering wheel I can feel when the heat pump kicks on. Not unacceptable but noticable.

 

[jwrezz]

I have not had to use the heat yet, only the heated seats and steering wheel. I can say that a couple weeks ago, when it was unusually hot for autumn, my co worker came out at the same time as me. I had started the hvac before I got into the truck. He said "this is the new, all electric f150?" my reply of "yes" had him ask "why is it so noisy?" As I got closer, I said it must be that I have the AC on. It can get quite loud when it needs to. I'm sure working in reverse, it'll be the same for the heat. I'll try it tomorrow morning. Heat pumps have gotten way more efficient in recent times. Below 0F isn't a big deal for home units. Maybe Ford made the switch without using the latest tech?

 

[F150guy]

I have a 24.

I never use Auto. Can't stand it. I prefer controlling the HVAC completely manual. Despite that it requires me hitting various menu items. But I can do it pretty quickly.

With that said, the Heat and AC icons will light up still automatically (annoys me to no end) driven by the temperature setting I also set manually. If I set it higher than ambient cabin temp, Heat lights up if I had it off. If I set temp lower AC lights up if I had it off. But Heat and AC icons seem to stay off if I turn them off a second time. At that point I think I have full control of all of the controls. It all starts over if I restart truck.

I switch the vents manually as needed. This is my preference.

I think I've hit Max defrost only once.

And my info button also says the only cabin heat is resistive like others mentioned. But I hear the Fans for heat pump activate if I change the temp or cabin fan to more extreme settings and outside the fans are quite loud when doing so.

 

[RocketGhost]

Only 42F here this morning...not even cold yet. But with the truck on "Auto" and temp set to 74F it still never got warm. Also, the windshield gets foggy.

So two questions:

Why do I have to crank the temp up so high to get warmth in the cabin? ALL my prior trucks I would set to 68-70F and stay comfy.

Why does "Auto" mode still require me to select A/C to get the compressor to clear the fog off the windshield?

I don't know the ins and outs of the Lightning's system. But here's some thoughts and guesses:

A heat pump in heating mode does not dehumidify air. Nor does resistive heat. To dehumidify air you need a cold surface to condense moisture. When a heat pump heats, the cold surface is going to be the exterior condenser and the internal evaporator is hot. When cooling it's the opposite. The inside evaporator coils are cold and condense moisture in the cabin air.

Traditional vehicles that heat the cabin with engine heat will turn on the a/c compressor in defrost mode. It cools the air at the evaporator to condense moisture and then heats it with the heater core before it is blown into the cabin.

Your truck doesn't know when the air in the cabin is humid. It will use the heat pump to heat the air to your temperature setpoint and that's it. The only way it knows that the air is humid is when you hit defrost and tell it you want to dehumidify. I'm guessing that pushing the a/c button is telling it the same thing and cools air at the evaporator to condense moisture and then reheats it at the heater core (this is an assumption and wild guess, I'm guessing your truck still has resistive heat capability).

I suspect the issue comes down to how the truck is programmed to maximize efficiency. It's going to use as little energy as possible to heat the cabin to your setpoint. It may not heat the air as fast as it could, nor will it dehumidify since it will have to use energy to reheat the air. Also the auto intensity setting (the three dots) is a factor. One dot isn't going to blow much air, so even if the incoming air is dry you're not getting much of it.

You probably just have to do what you've been doing. If it's foggy turn on defrost or select a/c so the air is dried. Setting auto to a higher intensity may help too.

Fun fact: I had a BMW with a windshield fog sensor. It would detect (in theory) fog on the windshield and defrost if needed.

My idea for an advanced system would be ambient and exterior humidity sensors. The computer could calculate the dew point and control the system accordingly to prevent interior fogging or just general stuffiness.

 

[Heliian]

Also, frost happens even above 0C/32F.

Water freezes at 0 c.

Thanks for coming to my Ted talk.

 

[Altivec]

If 74° isn't comfortable, set it to a higher number.

MAX defrost clears windows quickly.

For best comfort turn the HVAC on before you get in the truck. If you leave at the same time every day you can set a departure time.

Yours isn't the first thread focusing on how owners WANT the system to work. I find it more useful to figure out how to operate the system as it is installed.

I think you are missing the point. 76F is comfortable on a cold day and 64 is comfortable on a hot day. The point of “auto” is to stay comfortable without having to touch anything. Most of us have or have had many vehicles before so its not like we don’t understand how HVAC works. I’ve never had this issue on any other vehicle including Ford F150’s. I Set it to 70 once and rarely have to touch it again.

yes max defrost clears windows quickly but its obvious you don’t live in an area that is minus 30 on a nice winter day. Leaving it on max defrost makes the cabin uncomfortably hot so after the windows clear, either we need to set the hvac manually or press auto. If I press auto, the heat all goes to the floor. After a few minutes the windshield cools off with -30 winds hitting it. The dew point at those temps is very low so simply breathing towards the windshield causes it to fog. So every few minutes I need to switch back to max defrost and then repeat back to auto. It’s no fun becoming a slave to HVAC.

Yes the A/c compressor is on to dry the air but that does little if its all directed to the floor. Every other vehicle i’ve had always pushed a bit of air to the windshield. This little bit of air basically creates a thin warm dry barrier preventing our breath from hitting the cold windshield and fogging it. Not rocket science. It’s worked for over a decade including at Ford. Don’t know if the HVAC guy was sick and didn’t show up to work the day they were implementing hvac on the lightning

 

[MaintGrl]

I'm not trying to defrost (yet). I need to defog. "Auto" mode in every other vehicle I've owned over the last 30 years would automatically take care of that by using the compressor when necessary. This truck does not seem to do that. It's odd.

I did go to the climate screen and heat was selected on already. But the windows did not defog until I manually selected "A/C" and I also hit the "Auto" button until level 2 was selected. This entire thing is a joke and completely defeats the purpose of automatic climate control. At this point I honestly would rather have a basic non-automatic system with a temp knob, fan speed knob, and duct selection. Would be a lot simpler and more effective.

THANK YOU! Kinda what I've been sayin all along. This HVAC system is way too complex....for what it needs to do.

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