[FocusKnot]

Problems with the resistor block would affect speeds 1, 2, and 3. In speed 4, the power goes directly to the fan. If the fan is bad (shorted out) it will blow the fuse in position 4.

Unplug the fan connector and measure the voltage on the plug with the blower switch in position 4. If you are getting full battery voltage at the connector then the blower is most likely bad because you already know that if it is plugged in it blows the fuse.

This is a typical blower wiring diagram for the Focus. Yours may vary slightly.

 

[FocusKnot]

^^^Yes, that.

There is thermal fuse on the resistor block. If during your tests (after you put in the new block) you left the fan switch in position 1, 2, or 3 very long, it will pop the thermal fuse. Hopefully you did not ruin it and all you need is a new blower.

 

[FocusKnot]

Sorry you didn't get an answer DMCH82BL8. For some reason I didn't get a notification of your post to this thread. I just saw this and you may have already fixed it by now.

You are correct. Your problem would be a bad resistor pack. The position 1 resistor is burned out. That would explain the A/C clutch on and blower off in position 1. The opposite would happen in positions 2, 3, and 4. In the circuit diagram above, the wire going off to the right of the resistor block is what tells the A/C circuit that the blower fan is on and allows the compressor clutch to engage.