The Difference Between MDL & AGC Fusesby John Walker
Fuses operate within an electrical circuit to monitor the amount of amperage traveling the circuit. Electronics from vehicle computers to home stereos use different types of fuses to protect the equipment. The fuse has a metal point that melts or breaks when the set number of amps is exceeded. Two main types of interrupt fuses are MDL and AGC.
The AGC fuse type is a fast-acting glass tube fuse. Upon circuit overload, the fuse will almost immediately sever the power connection, protecting valuable electronics. In an area where amps fluctuate moderately, you will want to use an MDL fuse type. MDL has a slow interrupt speed, allowing for minor and short jumps in amps without causing the fuse to break.
MDL fuses are available in amp ratings ranging from 1/16 to 20 amps. AGC fuses have a larger range, from 1/20 amps to 40 amps. The dimensions of the fuses are identical for the various sizes.
You can use either fuse within a circuit. Before choosing an AGC or MDL type fuse, you need to identify the electrical needs of your component (e.g. radio, vehicle electronics, etc.) and the line. If there will be fluctuations in the line, choose an MDL fuse; however, if the lines are stable and the equipment is highly valuable, you will want to use an AGC fuse.