2020 Lariat. 86k miles. SCab.
Due to summer heat, and having often to drive into the sun in the afternoon, I'm finding the air flow from the AC vents is not what I consider adequate.
I have the speed set to '7' (as high as it goes) and AC temp to lowest setting. I have the vents set to torso and feet only. The dual zone is off.
I've checked that the cabin filter is not restricted (it's a non-HEPA) unit. The interior AC coil is not blocked. The exterior intake vents at the base of the windshield are not blocked. The fan speeds change audibly as I go through the numbers.

Maybe don't have enough charge in the system and the air could be colder? (if I put an IR scanner at the ducts, what temp should I see)

Mostly though it seems like there's just not enough airflow coming from the vents.

What else should I look at?

 

Park it, turn it off. If you see a large, large puddle of condensation water it could be that your system is freezing up blocking the flow. Does the airflow sound muffled?

 

You are kind of asking two questions I think. Is the airflow adequate and is the discharge temperature low enough to cool. looking for a puddle is an indication that the evaporator coil in the dash is cooling and condensing moisture in the air. If the fan increases / decreases speed when you adjust it low to high and notice a difference, I'd say that's good . However on these trucks there is a history of the blend doors in the dash sticking or failing.
The only way to check the refrigerant temperature reliably is to put the gauges on it and read the pressures and compare to the charts. You failed to state what truck you have but if it's a super crew and I suspect in a super cab the A/C system is borderline inadequate. I just added 1234YF refrigerant to mine a few weeks ago. I added about 6 ozs. of refrigerant to get to 40 deg at the evaporator.coil. It is colder at the vents but on a hot 90+ day I still need to run on recirc. to cool the interior before adjusting down still running the fan about 3/4 speed. One more note since the A/C always seemed weak I suspect the initial charge from the factory is less than ideal.

 

I am having the same problem. What I found out is it may be freezing up or if you google it there are lots of known problems with the evaporator temperature sensor failures. What I found with mine is driving at highway speeds when this happens I will turn off the ac but don’t touch the fan setting. Higher fan settings works better. In about 5 minutes or so the fan speed will rise back to normal. Mot sure if the evaporator is thawing or its hust the sensor warming up. When the fanis back to full air flow you can turn the ac back on and it will get cold again for 10 minutes or half an hour or so. Repeat again when air flow decreases. I am not sure if the evaporator is freezing or the thermistor that is the sensor on the evaporator is wonky. If you google this there is a lot of information and YouTube videos ranging from hacks to doing a full repair which means pulling the heater box which is a 10 hour job and includes pulling the dash. Some of the hack videos are done on other Fords and I have not found specifics for the F150.

i would like to try getting Forscan setting up on my laptop and I believe that we should be able to read the temperature on the evaporator core temperature sensor. Should it be incorrect hacks include installing a new sensor on the outside of the heater box or making a hole in the heater box. One fellow on a Superduty installed a resister in series with the connections on the wire harness. I do not know how to find the wire and connections to my heater box to the sensor. If someone had manuals or diagrams to find this connection that would be great, my truck is a 2018. I think the best way I should proceed would bevto get Forscan to read the temperature of the sensor when the ac is not functioning.

 

If the evaporator is freezing up you have a low refrigerant condition.

 

Refrigerant has been checked. Again that is why I should get Forscan running but I will need to purchase an OBDII connection for that. I would like to see what the evaporator temperature sensor is doing.

 

No big puddle after parking it.
It's fairly low humidity here in NM (20% after a rain, even less if no rain), that to say, doesn't it take a fairly high ambient humidity to freeze?
Airflow doesn't sound muffled, just not enough airflow.

Thanks for the input.

 

Super Crew.
Yes, two questions actually. The fan speed is the main question, and temp output the secondary question.
No puddles after driving.
Fan speed doesn't change by itself. But I can hear it change as I manually change speeds.
If blend doors are the issue, wouldn't air tend to be stronger out of some registers than others, given a set fan speed?
I've had the truck about 1.5 years, I don't remember having this issue last summer. But is at least 5 years from the factory.
I guess I'll have to find someone w/ gauges.
Thanks.

 

...... can you feel an increase at the vents?
If blend doors are the issue, wouldn't air tend to be stronger out of some registers than others, given a set fan speed? yes check to see if the air output changes when you select defrost - center - floor. If not or the air is constant on more than one outlet the blend doors may be the cause.
I've had the truck about 1.5 years, I don't remember having this issue last summer. But is at least 5 years from the factory. has the A/C been checked since? possibly a low charge or leak in the system.
Thanks.[/QUOTE]

 

I have noticed considerable more air coming from my vents if I have dash vent only selected and not dash vents and feet. Give that a try and see if it helps.

Good luck

Tom