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So tell me, are you using protection?

By Roy, BAT Auto Technical

All electrical circuits are protected against excessive loads which might occur due to shorts or overloads in the circuit. Such protection is provided by, fusible links, circuit breakers, fuses.

Fusible links are incorporated into the vehicles wiring harness and are used in circuits that are not normally fused. Each link is four gauge sizes smaller that the wire it is designed to protect and most are marked on the insulation with the wire gauge size because the heavy insulation makes the link appear a heavier gauge that it actually is.
Engine wiring harnesses incorporate several fusible links. The same size link with special insulation must be used when replacing a fusible link.
Some places that a fusible link might originate are, the starter solenoid battery terminal, The alternator warning light, the battery positive post of the alternator, junction block(s) at locations like, inner fender well, radiator support, and front cowl. A new fusible link can be installed, after the short circuit is located and repaired.

To do so one should:

1. Disconnect battery ground cable. (Don't forget the safety glasses.)(Protection)
2. Disconnect the defective fusible link.
3. Cut the defective link directly behind the connector.
4. If the crimp connector that's provided with the new link is not a type that will seal the connection cut if off and replace with a heat to seal crimp connector.
5. Strip approximately ˝" of insulation from the harness wire.
6. Crimp and seal the new fusible link to the harness wire.
7. Connect the new link to the connector that the old one was disconnected from.
8. Connect the battery ground cable.

Never replace a fusible link with standard wire! If this is done there is no protection for that circuit and a vehicle fire could well be the end result.

A circuit breaker is a protective device designed to open the circuit when the circuit load is greater than the rating of the breaker. If there is a short or any other type of overload in the circuit the excess current draw will open the circuit breaker, the breaker will automatically reset and if the problem is still present will open again. The breaker will continue this cycle until the problem is found and corrected, or due to the excessive cycling the breaker will become damaged and replacement of the breaker is then necessary. Never replace a circuit breaker with one of a higher (amps) rating! Doing this will also cause a lost of circuit protection and again a vehicle fire could be the result!

The most common protection of an electrical circuit is the fuse. Whenever there is an excessive current draw in the circuit, the fusible element of the fuse will melt and open the circuit. The disadvantage of the fuse is that it is a one-time protection and replacement is required Never replace a regular fuse with one of a higher (amp) rating or with a circuit breaker. (Not even one of the same (amp) rating.) The fuse is designed as a "fast" blow protection of the circuit. A circuit breaker does not operate as "fast" and circuit protection is compromised.

When doing circuit testing and the procedure calls for the use of a jumper wire the best protection is to use a jumper wire built with the same circuit protection as that of the circuit you will be testing. If you were testing the fuel pump circuit and the chart said to jump B+ (battery positive) to the circuit, and the normal protection for the circuit was a 20-amp fuse, then use a jumper wire with an in-line 20-amp fuse. You can build a jumper wire with an in-line fuse holder and keep an assortment of different size (amp) fuses, then check the circuit diagram to see which fuse to use for that circuit.

The idea is simple, learn what is protecting any circuit you work on, or repair and use that protection while doing any testing or repairs…

rdb

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