Not able to get high a/c fan output while driving.

When I start my 2011 Prius I can usually get the highest fan speed going while it's in park but once I start driving it will put out air closer to a low or medium speed and I can hear/feel it fluctuating up and down. If I put the car back into park I can eventually get it to put out high speed air but it takes a few minutes. I suspect it's a bad blower motor and/or resistor but the fluctuating up and down only while driving isn't a symptom I'm seeing others experiencing. Any idea what this could be?

 

I should add that after about 25 minutes of running, the A/C seems to work normally.

 

And sometimes if I set the fan to the lowest speed for about a minute, the issue will be resolved.

 

The highest fan speed fluctuates whether it's in auto mode or not. The fan speed goes up and down incrementally with the bar graph but the speed still fluctuates up and down.

That actually is good news about the resistor, thanks!

 

I checked and cleaned the cabin filter but while it was removed I noticed the fan speed was still fluctuating up and down.

I'll look into the blend door and air routing servos.

I'm guessing it's not overheating since it takes around 20 minutes or so for the fans to finally kick up to a fast speed and then it's generally fine until the car is turned off for a couple of hours. Also I have an OBD scanner and I've never had any codes that suggest overheating.

I thought maybe it was the auxiliary battery since it's fairly old and I've been having random intermittent electrical issues like windows going back down while I'm trying to put them up and the bluetooth disconnecting and then reconnecting about once a week. The battery looks like it's in good health though.

 

One other thing that I remembered was once during the last winter here I turned on the heat and it wouldn't pump out hot air until I turned the HVAC system off and on a couple times, then is started pumping hot air immediately. At that point I hadn't had any fan speed issues and I thought it was just a weird electrical thing like the windows/bluetooth.

 

I replaced the blower motor and that seems to have done the trick. The spinning cylinder seemed fine so I'm guessing it was the resistor. Thanks for the help!