<VV> Blowing fuses

David Neale david.neale3 at ntlworld.com
Sun May 3 19:15:31 EDT 2020

Hugo, the 12 volt test bulb cannot, and will not, blow. The fuse is a piece of metal, most commonly a piece of wire, of very low resistance, intentionally designed and dimensioned to be the weak link in the circuit. The heavier the current it must pass without fusing, the thicker the wire will be. The circuit voltage is immaterial here. Every fuse has an upper voltage limit; in the case of our Corvair fuses, many times the normal system voltage. Note that a 10 amp fuse for the Corvair will be as happy as a pig in you-know-what if inserted into a 24 volt system. The fuse doesn't care what the system voltage is.  A bulb has a high resistance when hot, attained extremely quickly here. Placing the bulb across the fuse terminals in this case merely presents the bulb with a nominal positive 12 volts on one side, and in the fault condition subject of this discussion, essentially an earth, or ground. In other words, just what the bulb requires, just what it is designed for.  If this explanation doesn't satisfy you, use one of your 24 volt coach bulbs, instead. It'll still light up, albeit dimly.

David Neale, in leafy Leicestershire, England.

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