Hello everyone. I've got a 2009 F150 Lariat XLT 4x4 5.4L.
My truck has the Auto Temp Control Dual Passenger system with heated seats only.. I lost control of the Blower Motor. Always on High Fan. Then fan quit working all together. I replaced the Dash control unit after checking all fuses #15 passenger side fuse panel and all relays for blower motor and HVAC system including AC Clutch, NO JOY. I then replace the Blower Motor Speed Controller. Fan started working, but on High again "without" control of it. At same time AC Clutch would no longer engage. For ****s and Giggles I replaced the Blower Motor. NO JOY. At this point, I'm out of ideas and super frustrated. There was a thread on this issue but no-one has found a fix or at least posted one. Please help. Retired Navy 20 yrs as an aircraft mechanic and disabled. Really need some help in this one. Thank You All...

 

Did you replace the blower motor resistor?

https://www.tascaparts.com/oem-parts...00bC12OC1mbGV4

BLOWER MOTOR RESISTOR - Ford (3F2Z-18591-AA)

 

Yes I did. It's called a speed controller now from what I understand. Bolts up to air box with a 4 pin straight connector. It has 4 aluminum fins that go into air box. The inside is a circuit card with the 4 pins that go into the connector housing. After I changed it out the fan would come on real high and then slow slightly after 2-3 seconds. Also the AC Clutch wouldn't engage. AC compressor and clutch were working fine just prior to blower motor quitting. Changed speed controller as I said and fan began to work again as described above. Really scratching my head over it. I'm wondering if perhaps there are any temperature sensors in the system for auto temp, hi temp limit, and temp anticipator. I worked on aircraft air conditioning and we had sensors such as these. I wouldn't know exactly where they are and which ones do what as I have no schematics etc. Thank you for responding. Very much appreciate it.