Circuit Protection Devices

Saturn vehicles use four types of circuit protection devices, minifuses, maxifuses, circuit breakers, and fusible links. The minifuses and maxifuses function similar to the current autofuse. The primary purpose of a fuse is to protect the wiring during short circuit conditions. In some cases, the fuse rating is intentionally undersized in order to protect the device to which the wiring is connected. Fuse rating selection is a function of total load current, nuisance blow safety factor, cable gage size, temperature, and circuit length.

A fuse is a device that, by the melting of its element, opens an electrical circuit, when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse is replaced after the circuit malfunction is repaired. Since the fuse functions by the melting of its element, it is a temperature sensitive device. This means that the fuse is affected by changes in ambient temperature, external heat sources (such as other fuses), and external heat sinks (such as conducting wires).

Minifuses
The minifuse is the most common circuit protection device in a Saturn vehicle. Minifuses are available in ratings from 5-30 amps and are located both in the underhood fuse block (UHFB) and the instrument panel fuse block (IPFB).

Maxifuses
The maxifuse is a relatively new circuit protection device that is designed to be a serviceable replacement for the fusible link cables previously used in the automotive industry. It operates very similar to the minifuse except that the operating current is much higher. Maxifuses are available in 20-60 amp ratings. Currently, Saturn vehicles use 30 amp and 50 amp maxifuses. The blow characteristics have been designed to match cable temperature curves for overload conditions.

All maxifuses are located in the underhood fuse block (UHFB).

Circuit breaker
A circuit breaker is used to protect those circuits that can experience intermittent overloads (e.g., window motor stalling). There are two types of circuit breakers; cycling and non-cycling. The non-cycling circuit breaker will reset only after the overload condition is removed, while the cycling breaker will automatically reset after a certain time period. If the overload is still present, the cycling breaker will reopen and start the cycle over again.

Circuit breakers used on Saturn vehicles automatically reset.