How does cabin heating work?

[RLXXI]

We have a 23 XLT and a 24 Flash in the driveway, so one of each kind of heating system. We live in the Sierra foothills so while snow and ice are routine, butt-numbing cold (like we suffered in Michigan; I know of which I speak) is not.

Yes, resistive heat is almost instant-on and that's nice. Yes, there is some extra fan noise with the heat pump. But anyone that thinks one is significantly better than the other is mistaken. They both work just fine. Both are quiet and smooth when compared to ICE. Any difference between them in how they feel/perform is splitting hairs.

If you live in a place that has arctic cold then you might have a different experience.

The only key difference besides the components, battery charge, the old resistive system will draw it down way faster.

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[RLXXI]

Just got back, turned ac on, noted sound and feeling, nothing out of the ordinary. This time with heat on, no difference that I can hear or feel. None. Nada, Zip, Zilch difference.

Cooling works fine, heating works fine. It's worth noting no two vehicles will exhibit the exact same characteristics even if they are one behind the other on the assembly line.

 

[Firn]

Just got back, turned ac on, noted sound and feeling, nothing out of the ordinary. This time with heat on, no difference that I can hear or feel. None. Nada, Zip, Zilch difference.

Cooling works fine, heating works fine. It's worth noting no two vehicles will exhibit the exact same characteristics even if they are one behind the other on the assembly line.

The only thing I would say is that for the heat pump trucks the "AC" compressor will run, as will the exterior fan when making heat. For the resistive heater there will be no sound at all.

I'm not saying those are loud or unusual, just that there is no sound at all with the older trucks.

Edit: Aside from the interior cabin fan that is

 

[Firn]

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.

Fwiw the truck does have an interior humidity sensor.

 

[F150guy]

Only the seat, rear defrost, side mirrors and steering wheel heat are resistive 24>

Thank you. I agree.

I will say the steering wheel heat is inadequate. Starts off warm (not toasty) and then diminishes but stays on at barely above what your hand would generate for heat by itself. I keep forgetting to contact my dealer about it. Maybe this week.

 

[P-38]

Thank you. I agree.

I will say the steering wheel heat is inadequate. Starts off warm (not toasty) and then diminishes but stays on at barely above what your hand would generate for heat by itself. I keep forgetting to contact my dealer about it. Maybe this week.

You can adjust the steering wheel temp with forscan. Your dealer should be able to as well they just might need a little nudge to get them looking in the right place

 

[hb.sagen]

This will be the first winter for me. On any car I've had I have always used A/C in the winter to combat fogging inside. Will do so this winter too. Hope it works.

Filling the car with people and snow from shoes etc. always creates a fogging potential.

 

[jwrezz]

The only thing I would say is that for the heat pump trucks the "AC" compressor will run, as will the exterior fan when making heat. For the resistive heater there will be no sound at all.

I'm not saying those are loud or unusual, just that there is no sound at all with the older trucks.

Edit: Aside from the interior cabin fan that is

It also depends on how hard the system needs to work to overcome ambient temperature. Either way, cooling or heating the cabin, if it has to work harder it will definitely be louder. This is why I said on that unusually hot day in the Autumn when I had the AC on, sorry the cooling on, my truck was in its parking space as I was approaching it and my coworker said why is it so loud if it's an electric truck? But it wasn't the truck running it was the HVAC running. When I turn it on in my driveway and there isn't much of a difference between the outside and inside temperature, it's nearly silent.

 

[WXman]

This will be the first winter for me. On any car I've had I have always used A/C in the winter to combat fogging inside. Will do so this winter too. Hope it works.

Filling the car with people and snow from shoes etc. always creates a fogging potential.

Yes, have to use the A/C button to provide conditioned, dry air into the cabin for defogging. Works great, even on the Lightning.

I guess my main point is that it seems that on my '25 Flash, the "Auto" setting does not use the A/C automatically when there is moisture in the cabin and fog on the inside of the windshield. To me this seems very odd, and it's the first vehicle (out of 30+) that I've had that behaves this way. I guess this winter I'll just turn "Auto" off and use the controls manually.

 

[RickLightning]

The only thing I would say is that for the heat pump trucks the "AC" compressor will run, as will the exterior fan when making heat. For the resistive heater there will be no sound at all.

I'm not saying those are loud or unusual, just that there is no sound at all with the older trucks.

Edit: Aside from the interior cabin fan that is

Right. In summary, the Lightnings with heat pumps are dramatically noisier than those without. How noisy a vehicle is in the dead of summer as compared to the dead of winter is irrelevant...

Thank you. I agree.

I will say the steering wheel heat is inadequate. Starts off warm (not toasty) and then diminishes but stays on at barely above what your hand would generate for heat by itself. I keep forgetting to contact my dealer about it. Maybe this week.

The amount of heat will vary depending on the temperature.

 

[B177y]

Yes, have to use the A/C button to provide conditioned, dry air into the cabin for defogging. Works great, even on the Lightning.

I guess my main point is that it seems that on my '25 Flash, the "Auto" setting does not use the A/C automatically when there is moisture in the cabin and fog on the inside of the windshield. To me this seems very odd, and it's the first vehicle (out of 30+) that I've had that behaves this way. I guess this winter I'll just turn "Auto" off and use the controls manually.

In my '24 Pro with a heat pump, the AC toggles itself on and off constantly while in Auto mode. As soon as I think to myself, "Hmmm, there's some fog starting on the windows", it seems to turn itself on and the fog automagically goes away. If you get consistent fogging in Auto, I would suggest a trip to dealer service while you're under warranty as there may be an issue with your humidity sensor or some other component that is not working properly.

 

[RLXXI]

Right. In summary, the Lightnings with heat pumps are dramatically noisier than those without. How noisy a vehicle is in the dead of summer as compared to the dead of winter is irrelevant...



The amount of heat will vary depending on the temperature.

I guess my truck Is special then because it makes no difference in sound on my truck, I don't hear anything with it on. If I had to compare to my other truck, it's dead silent.

 

[RickLightning]

I guess my truck Is special then because it makes no difference in sound on my truck, I don't hear anything with it on. If I had to compare to my other truck, it's dead silent.

In the winter, my truck makes no noise running the heat. Your truck makes the same noise as it does in the summer. That noise, IN THE WINTER, is much louder than my truck's noise in the winter. Which of course you know, and understand.

 

[F150guy]

Right. In summary, the Lightnings with heat pumps are dramatically noisier than those without. How noisy a vehicle is in the dead of summer as compared to the dead of winter is irrelevant...



The amount of heat will vary depending on the temperature.

So my steering wheel temp also adjusts to environment temps? I was thinking it just has an initial temp (mild but never hot) and then it diminishes to barely mild according to software logic.

 

[RickLightning]

So my steering wheel temp also adjusts to environment temps? I was thinking it just has an initial temp (mild but never hot) and then it diminishes to barely mild according to software logic.

It heats up to around 90F, then cools, then heats, then cools. So if the vehicle is already 70F, it will run less than if the vehicle is 25F, and feel cooler to the driver.

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