I have a Ford Focus 2008. I am trying to install a manual switch to control the cooling fan because it is no longer working. My relay connections are perfect. But the 30 AMPs fuse in the cable that runs from +ve battery to PIN#30 in the relay keeps blowing out. Do I need a higher rated fuse or what?

 

As a reminder, fuses blow because there is current demand on the circuit that is beyond the rating of the fuse.

A wiring diagram would be very helpful at this point, but without on we can do some basic checks.

Does the fuse blow as soon as you install it or does the engine temp need to come up first?
Most circuits take power from the hot supply at the fuse panel , run it thru the fuse to the relay pin 30. If you have the relay out does the fuse still blow? If so, look under the fuse panel for a problem. If it blows only with the relay installed , the relay and/or wiring to the fan speed relay(s) has a problem.
Before going any further , the answers to the above questions can help determine where we go next. DEFINITELY NOT A LARGER AMP FUSE,

 

I kind of figured it out. I put in a 20 AMP fuse (between the battery +ve terminal to PIN #30 on the relay) and all is good.

 

A shortcut in this case may create some problems you were not anticipating.