This is an interesting problem. Blower fan does not function. Fuse, o.k., no power to the dashboard switch. I tore the dash apart today as far as I could go in the limited time that I had. How do you get the headlight pull rod out to get all of the dash trim off?

Does anyone know where I can come by a schematic on an expedient basis other than the dealer? This truck belongs to my youngest daughter and it is getting to be irritating for her to drive with no defroster on the icy night that we are having.

 

I had almost the same problem a few weeks ago but the ground on the swith went bad, I had to splice in a new ground strap on the black wire to make it work.
Try going to the library for a clymar book.
I have the official Ford schematic in a manual 4 inches thick and it did not help me sort out three or four wiring problem.

 

Did you put power to the motor to make sure it is ok? If the fan turns with external power, and you have voltage to the fan, it almost certainly is a ground problem.

 

If Ford did'nt "improve" the heat/ACsystem in 88 it should be wired the same as my 87. My 87 is wired from fuse to blower motor and from blower motor to blower resistor & blower switch on the dash. As hreed mentioned check for 12 volts at the blower motor under the hood. On my 87 it's a brown/orange stripe wire. Sounds like that Clymer manual that saintoc mentioned might come in handy for this. Have you tried turning the fan on & giving the blower motor a good whack? If that gets it going replace it.