This is the most common failure mode.
Ford f150 heater fan only works on high.
Most commonly the fan will only run on the highest setting.
This video highlights a common issue found on 2011 ford f150 pickups with automatic hvac systems when the blower fan speed becomes stuck on high speed.
4l3z 19a706 aa or napa part number.
Any obstructions or hindrances can blow the resistor quickly.
Fan kicks on about 30 seconds after vehicle is started and is extremely loud.
I thought i d contribute a couple pictures.
My fan was working on high only.
Correcting the problem is straight forward and requires replacement of the small resistor.
Articles how to s heater blower fan fix only high speed i did my search and found plenty of help.
This is a well documented problem and is caused by a failing blower motor resistor.
In other designs the failure of 1 resistor means you lose only one speed.
The 2004 2014 ford f 150 with manual temperature and fan controls may have problems with the the blower motor only blowing air on certain settings.
However most car makers bypass the blower motor resistor completely when you move the fan speed switch to high.
I would like to thank everyone who contributes information.
My truck ia a 1999 f150 with manual heat ac 115 000.
All you need to do is to replace the resistor ford part number.
You should check and make sure the blower motor is working properly not jammed or any obstructions preventing the free movement of the blade fins.
2010 ford f150 radiator fan seems to be running on high more than it should.
And yes the resistor is bypassed with the fan is on high.
Even kicks on when its a cooler day.