This should be fairly simple. I have uploaded a PDF file to Filesonic.com that contains both the Power Distribution Diagram for Fuse #64 and the Heater Circuits for your 2000 Ford Focus. You can download this file for FREE at the link below. Please note that if you do not have an account with Filesonic, you can still downdload the file for free, but you must use the "Slower Download" link at the bottom of the page. You will then see a timer running in about the center of the page. Once the timer runs out, it will give you a captcha code to enter in order to start the download. This file will only be available on Filesonic for 3 days, so you might want to save a copy to your computer for future reference.http://www.filesonic.com/file/3040758464/2000_Ford_Focus_Heater_Circuits.pdf
Once yo have the file, you can clearly see that the ONLY thing that is powered by that fuse is the blower motor. That makes this task very easy.
Most likely, the blower motor itself (or the solid state circuits built into it) are shorted. Here is how we PROVE it before going out and buy a blower motor:
1. Unplug the blower motor connector. Replace the fuse with the connector disconnected. If the fuse blows, then the GREEN/ORANGE wire between the fuse and the blower motor is shorted to ground. You will have to follow this wire from the blower motor back to the fuse block to find out where it is shorted.
2. If the fuse does not blow, then take a test light (make sure it uses an incandecent lamp - the LED type will not work for this purpose) and connect it between the GREEN/ORANGE wire (ignition switch ON) and the BLACK/RED wire at the blower motor connector. Using the blower motor speed control switch, the lamp should not light at all with the switch in the OFF position. Then it should light and get brighter with each step as you move the switch toward the HIGH position. If this all works as described, then we have just proven that all of the circuits are good and that you need to replace your blower motor.
3. If anything does not work exactly as described, tell me what it is doing that is different, and we can continue diagnosis if needed.
Hopefully, this is all the information you need, but if you do need anything else, please let me know.
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