What would cause the ecmb fuse to pop on a 1989 full size blazer?

There are only two things which cause fuses to "pop," or blow. 1. Electrical current flow [amps] in the circuit which exceed the amperage value of the fuse. This would be caused by a short circuit to ground, either inside the ecmb, or anywhere in the circuit wiring. 2. Very seldom, a fuse may be defective and simply fail "on its own."j3h.