FIRST, Take the 20AMP fuse out and put in the correct size. Putting in a larger size fuse can actually overheat the wire and cause a fire inside your car, if it doesn't blow the fuse first.
Look for -
#1 - a blown bulb in one of your brake lights
#2 - a blown bulb in a marker light (since they usually share the same bulb in the rear)
#3 - look for a wire that has either come loose, not reconnected properly or got pinched if you just changed a bulb
#4 - check the brake light switch attached to the brake pedal arm under the dash. If the switch has broken, the positive wire could be arcing against the brake arm lever when you push the pedal arm to make the brakes come on.
What is comes down to is this - when you apply the brakes, the positively charged wire is allowed to "ground" completing the circuit, instead of the electrical charge completing the circuit thru the bulb.
It is completing the circuit by grounding itself against something
"shorting out" the fuse which causes it to blow.
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