Fusible Link Wire
Frequently Asked Questions
- What is a FUSIBLE LINK?
- It is a piece of wire placed in a circuit that is designed to open that circuit when subjected to an extreme current overload. Its purpose is to minimize damage to the wiring system when an extreme overload occurs. It is identified by the words "Fusible Link" and gage size printed on the jacket.
- What is the CONDUCTOR made out of in a fusible link wire?
- The conductor in a fusible link wire is the same as regular primary wire (copper). It is not a low-melting-point copper conductor. It is approximately four wire gages smaller than the circuit wire leading up to it. Example: a 12 gage circuit wire would normally require a 16 gage fusible link.
- How does a fusible link BREAK DOWN in an electrical circuit?
- Since the fusible link is four wire gage sizes smaller than the circuit wire leading up to it, it will become much hotter in a dead short than the "lead-in" wire. When it reaches 1,000 degrees, it will separate and kill the circuit.
- Should a BURNED OUT fusible link be replaced?
- Do not replace a burned out fusible link until the cause of the problem is discovered and fixed. Failure to fix the problem first could allow damage to the wiring circuit and/or vehicle. After the cause of the burn out is identified and fixed, then a new fusible link can be installed.
- How do I know what GAGE SIZE and LENGTH fusible link wire to use?
- Since the automobile manufacturers have determined the proper gage size and proper wire length, use the same gage size and length as the original link wire. Usually, a fusible link wire will be approximately nine inches or less and is four wire gage sizes smaller than the circuit wire leading to it.
- What is different about the JACKET INSULATION used for fusible link wire?
- Per S.A.E. specifications, fusible link wire must be made out of high temperature, cross linked polyethylene (SXL). In a "dead short" situation, this high temperature jacked will remain intact while the conductor will heat up and separate.
- Are the little "FLAGS" on some fusible links the "built-in" fuse?
- No, they are only plastic or rubber identification flags and are not part of the electrical circuit. Some fusible links have little "boxes", but they are also not part of the circuit and are used for identification only.
- What type of TERMINALS should be used for fusible links?
- Insulated butt connectors that are equal to the current load of the circuit being protected should be used. These butt connectors should be covered with heat-shrink material to contain the heat generated by the current overloads. "Solid Seal" and/or "Crimp and Seal" heat shrink butt connector terminals are ideal for these terminations. Failure to use terminals with heat shrink material could allow heat to escape and could prevent or slow down the heating up and breakdown of the conductor.
- Can a FUSE or CIRCUIT BREAKER be replaced by a fusible link?
- No. Fuses and circuit breakers are put in a circuit for a reason. Replacing these "quick burn" products with a "slow burn" product could cause damage to a vehicle's wiring system or other electrical accessories.
Additional fusible link wire information can be obtained from S.A.E. bulletins J156 and J1128.