The fan is under the hood, near the firewall on the passenger side.

You still haven’t answered whether the fan runs when heat is selected. For the moment, the temperature of the air from ducts doesn’t even matter. I’m mostly interested whether you get airflow or not. And if no airflow, can you at least hear the fan running?

 

As far as I know, the fan does not run. There is zero airflow from the vents in any setting, whether heat or a/c. Doesn’t matter if it’s defrost, fan, etc. I don’t recall hearing any additional fan in particular but I will check that specifically when I’m able to get to it again. If the fan is not running, what would be your next move to troubleshoot?

 

Wiring diagrams here, see page 146. Additional troubleshooting on other pages, too:

https://www.garysgaragemahal.com/ac-heater.html





To troubleshoot, turn the key to Run but don't start the engine. On the HVAC control panel, slide the bottom lever to Floor. Select the fan speed to Hi. The fan should run. Even if you're not feeling any airflow, you should be able to hear the fan. If not, check fuse #9. If good, remove the plug from the fan motor. Check for battery power on the orange wire and a good ground on the black wire. If you've got good power and ground, remove the fan motor and make sure it's not jammed with debris (more on that below).

If no power on the orange wire, slide the selector lever back and forth a few times, and try any position other than OFF. If still no power, the selector switch is bad.

If power is good on the orange wire, but no ground on the black wire with HI selected, the blower switch is likely at fault.

If the fan runs but only on HI, the resistor pack is probably bad. These resistors are bypassed with HI selected, and are a common failure.

More details about the resistor pack here, including the potential for starting a fire. Even if the fan magically starts working, remove the resistor pack and fan motor for a good cleaning. Both are very easy to remove. If your truck has been sitting for any amount of time, this is pretty much mandatory due to the fire risk. The resistor coils glow red hot in any setting but HI:

https://www.ford-trucks.com/forums/1...n-the-cab.html


Photo credit to "Hardward"

 

Great information, thanks very much. I’ll look into all of this and try those methods, maybe I can track it down. I fired up the truck last night and let it idle for a while, I couldn’t quite tell if the heater fan was running. I know inside the cab I never heard the fan kick on.