Fan Speed Dropping as I Raise The Temperature

[nurspouse]

For climate control, I almost always have "Auto" off, and manually set the fan speed to 5.

The problem I'm seeing - sometimes I increase the temperature (too cold outside). I still want air on my face, but I want it to be warmer.

What I'm seeing: Often, past a certain temperature, the air blowing from the front vents drops when I raise the temperature, causing a lot of discomfort.

To reproduce:

1. Turn off "Auto"

2. Turn off AC

3. Set temperature to lowest.

4. Set fan speed to 5.

5. Set air to come only from top vents

Put your hand in front of the driver air vent (the one in the middle) to gauge the amount of air coming out. With other hand, raise the temperature to something pretty high. After a few seconds, you'll see a noticeable drop in the fan speed.

(I think it will eventually return to the usual fan speed once the temperature has been reached, but that will take a long time).

I assume this is normal?

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[Mach-Lee]

Manual fan speed is still a request, i.e. a setting of 5 is not a constant speed and will still depend on conditions. Think of it more like a setting of "more" or "less" fan speed instead of an absolute setting.

When you increase the set temperature, the cooling demand would be less, so the fan speed would reduce. Which is normal behavior.

I always say this, but it's my personal recommendation to leave the HVAC in the AUTO mode and only adjust the temperature up and down to comfort. That will give you the most efficient air conditioning.

 

[nurspouse]

That's just terrible. The whole point of disabling auto is not to have "magic" occur. So if I set it to blow only from the top vents, it can arbitrarily decide to also blow from the bottom vents?

The primary goal is to have air on my face. Being at the right temperature but without air on my face isn't going to help. Right now, if I raise the temperature (i.e. increase heat), I need to also adjust the fan speed to the absolute max just to get a decent amount of air on my face. And then 3-20 minutes later, it will decide to increase the fan speed and I'll have to adjust the speed down.

Having a constant fan speed has been the norm for decades. Why would they change that?

 

[NY_Cade69]

OTB, Perhaps try a USB powered fan?

 

[nurspouse]

OTB, Perhaps try a USB powered fan?

I actually searched for one, but couldn't find any that I can attach easily somewhere in the front.

I do have a USB fan for the back seats - my kid kept complaining about not getting enough air (and with the rough ride the car is, no air just adds to motion sickness). I attached it to the passenger side headrest. Fortunately, when I'm driving alone, I can rotate the fan to point to my head (side, not face, but still better than nothing).

The problem, though, is that the temperature of the air from the USB fan is the same as the ambient temperature. So if it's quite cold, I'll get cold air. Even worse, if it's hot, I'll get hot air. At least until the car comes to the right temperature, which could take a long time.

 

[nurspouse]

I always say this, but it's my personal recommendation to leave the HVAC in the AUTO mode and only adjust the temperature up and down to comfort. That will give you the most efficient air conditioning.

I'll add that this has been far from my experience in both of my cars. AUTO is great to get the full car at a certain temperature. But when I'm the only occupant, getting the right temperature air blowing right on me is much, much faster (seconds as opposed to minutes).

It's why people have fans at home. On a warm day, a fan actually makes the room warmer due to the heat from the motor. But the reason people turn it on is because it makes the person cooler (while making the room warmer). I refused to believe this until I actually took measurements.

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