Re: What's the difference between SFE and AGC fuses?
SFE fuses are 'automotive', rated only to interrupt 32 volts. The length depends on their current rating, ranging from 5/8" for a SFE-4, to 1-7/16" for a SFE-30. AGC fuses are 'general purpose', they are always 1/4" by 1-1/4", available in 250V ratings to 10 amps, & 32V ratings to 30 amps. An AGC-20 is the same length, & pretty much interchanges with an SFE-20. Both types are "fast acting", but according to my Buss charts, the SFE is a little faster. An AGC-20 is rated to carry 27 amps for up to 60 minutes, while an SFE-20 will blow in under 2 minutes. However, the 60 minutes is given as a maximum, while the 2 minutes is apparently typical, so that may not be an accurate comparison.
SFE Glass fuses are designed to specifications set by the Society of Fuse Engineers. All are 1/4 inch in diameter, but vary in length according to the ampere rating to ensure accurate fuse replacement. Both AG and SFE fuses were designed into North American vehicles prior to 1981. Glass fuses are also used for auto accessory applications.
AGC = Automotive Glass Cartridge