If the fuse blows right away, you're one step ahead of electronics problems diagnostics. That means it's not an INTERMITTENT problem, and you can catch it in the act.
Electricity flow is just like water in a hose (
tastes a little different, especially if you use an organic analog multimeter (pic below), instead of a digital multimeter - louder scream = higher voltage) :
You have a hose with a sprayer on the end.
Screw it on the spigot, you still don't have flow yet, till you turn on the valve / switch.
Still it's not 'flowing'; only the hose is energized.
Now put an imaginary water wheel in the middle of the hose.
It doesn't turn until the 'ground' is made (squeeze the handle on the sprayer nozzle).
Let only a little water out (bad ground), and the wheel turns slowly (or the light bulb is dimly lit).
Too much flow (
your problem) makes the wheel spin FASTER than it's supposed to - or, if it's a light bulb (nothing more than a glorified fuse), guess what happens? POP goes the fuse.
What makes too much flow? How 'bout a cut in the hose downstream of the wheel, along with the sprayer on? Yup. This would be like the insulation stripped, and making contact with the frame.
Do this:
At the fuseholder, determine the polarity. You will have to physically follow the (-) side, to the device (s).
Or, determine from FSM, where the (-) goes (you referred to a splice, which means that it's a compound circuit, with several sprayers on the ends of the [divided] hose). Work backwards from each one, to the splice, then to the (-) of the fuseholder. Somewhere, you're gonna' find a cut in the hose.
Sounds like a pain. It is. But there's no better way to get to know YOUR car. THink of it as a sight-seeing trip.
And there's other analogies, like hose / pipe size, depending on how much current (water wheel size) is needed to turn the wheel / fan, etc., etc., ...
A few guys here on the boards KNOW there cars, from doin' this kind of stuff. Knowledge beats $$ ALL DAY LONG.
Teacher
OUT 
ed.:
The other guy said it "may be less costly to use a DMM ... ". Trust me - ain't no 'maybe' about it; it IS-a-be
