fuseable links to starter
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There actually is not direct ampere rating for a fusible link to fail. The conditions under which a fusible link overheats and opens is more of a current/time curve. The fusible links at the starter, for example, will pass a constant 15A without even getting warm. They will pass 20A indefinitely with a bit of heating. As the current rises above 20A, the amount of heat generated increases. If the load is over 30A and is not reduced intermittently or periodically, the link will fail, but after quite a long time. At 40A, the link will fail more quickly. If periodic loads reach 50-60A for brief periods, the link will heat, but not fail. A constant 50A will cause the link to fail within a short time (less than 60 seconds).
So, as you may be able to understand, there is no definite failure rating, as there would be with a eutectic alloy fuse element. Later vehicles that eliminated fusible links typically replaced them in the body and chassis power circuits with 60A or 80A fuses. At those current levels, the fuses would open within seconds, and the circuits would be deenrgized. With a fusible link, temporary overloads are tolerated briefly, but the load circuit wiring is still protected, in a slightly different manner. Fusible links are more forgiving, like me.
If yours have failed, there has probably been some significant overloading for some time, unless you had a catastrpohic event like a pinched wire. You can safely replace them with a 6-8" length of AWG 16 copper wire. This wire must be crimped to the power source wire and load wire. The crimped connections should then be sealed against corrosion.
NOTE: Almost all other electrical connections on a vehicle should be soldered, but common lead/tin alloy solder is useless for a fusible link, and could present some danger. Since the link will occasionally heat under normal operating conditions, the solder can melt. When this occurs, the connection is altered, and the heating at the connection can increase or voltage drop can lower circuit voltage (I/R drop). This can increase current to some devices (like motors) to compensate for the reduced voltage, and a cascade effect can occur causing component failure. Additionally, the molten solder can wick along the link and effectively increase the size (guage) of the wire. This will defeat the protection of the link.
Usually, the only acceptable method to connect wires on the vehicle is a soldered joint, but this is one of the rare exceptions.
So, as you may be able to understand, there is no definite failure rating, as there would be with a eutectic alloy fuse element. Later vehicles that eliminated fusible links typically replaced them in the body and chassis power circuits with 60A or 80A fuses. At those current levels, the fuses would open within seconds, and the circuits would be deenrgized. With a fusible link, temporary overloads are tolerated briefly, but the load circuit wiring is still protected, in a slightly different manner. Fusible links are more forgiving, like me.
If yours have failed, there has probably been some significant overloading for some time, unless you had a catastrpohic event like a pinched wire. You can safely replace them with a 6-8" length of AWG 16 copper wire. This wire must be crimped to the power source wire and load wire. The crimped connections should then be sealed against corrosion.
NOTE: Almost all other electrical connections on a vehicle should be soldered, but common lead/tin alloy solder is useless for a fusible link, and could present some danger. Since the link will occasionally heat under normal operating conditions, the solder can melt. When this occurs, the connection is altered, and the heating at the connection can increase or voltage drop can lower circuit voltage (I/R drop). This can increase current to some devices (like motors) to compensate for the reduced voltage, and a cascade effect can occur causing component failure. Additionally, the molten solder can wick along the link and effectively increase the size (guage) of the wire. This will defeat the protection of the link.
Usually, the only acceptable method to connect wires on the vehicle is a soldered joint, but this is one of the rare exceptions.
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