I have a, new to me, 2018 XLT with almost 70k miles on it. No relevant mods have been made to the truck. I believe I'm having an issue with the blower motor, but I haven't been able to find anyone else that has had this specific problem and the dealership has said this isn't a recognized issue. Vehicle is not under warranty.

When I start the vehicle and turn the fan speed all the way up everything runs normally for a couple of minutes, then the fan speed starts to slow down to barely a trickle and I functionally have no air conditioning or air from a fan. During this time the fan speed display is still maxed out and the small amount of air coming out will remain cold the entire time. This problem occurs regardless of the initial set fan speed, it just shows up quicker when the fan is turned up all the way.

A few notes:
- The rate at which the fan speed reduces seems correlated with driving the vehicle. If I turn the vehicle on and sit at idle with the A/C on full blast it will take 10-15 minutes for the fan speed to get down to barely anything.
-Turning the truck off or shutting off the climate control for half an hour or so will "recharge" the fan and allow it to run at full speed for a few minutes when restarted.
-This problem occurs regardless of where the air is being diverted to (feet, face, defrost).
- The dealership confirmed that all software is up to date.
- If I blast the A/C until the fan slows down, then switch to hot air the fan speed eventually ramps up the expected air output. If I then switch to A/C the fan speed will decrease itself to barely anything over a few minutes.

The dealership said all power to the blower motor was showing up as normal and recommended recharging the freon and adding dye to track down a leak, while also saying that they don't expect this to fix any of the actual problem I brought the truck in for.

I'm all ears if anyone has seen this issue, knows additional diagnosis points that I should check, or has any advice to give.

 

Based on the symptoms you describe I would suspect a low refrigerant charge and the evaporator is freezing up. I would go to a good AC service shop and have it checked.

 

Thanks. Should a shop be able to test the current charge of the refrigerant and tell me if the pressure is currently low?

 

Yes, they can check the pressure in the AC system as well as test it for leaks.

 

If this is new to you, seems the Dealer would have offered a 30 day warranty from the start. If not, I'd bet it was traded in because of this known issue. That said, I'd Google your area for good reviews on Auto A/C repair, the Dealer would be my last stop if it was coming out of my own pocket. Good luck, hopefully it is an easy fix.

 

I would check it for codes. The HVAC module may have a stored trouble code.

The OP said the blower slows down not a reduction in airflow. That’s a difference. I assume he means the blower is slowing down in the same manner if he reduced it to it’s lowest setting. If it was airflow the blower would be wide open but he wouldn’t feel anything coming out the vents.

My line of thought is there is a problem with the HVAC module.

 

I forget on this vehicle if you can access the blower motor behind the glove box. Possibly you could inspect the motor and cage. Could even try to pull it when it is slowed down to inspect in the bad state.

 

I took the truck to an A/C shop and it turns out the freon was contaminated, there was about 75% 1234YF and then the rest was RF134A and a little bit of air. After getting it bled, flushed out, and recharged everything is working great. Thanks for the help, all!