In one form, tester for an electrical system, such as for a vehicle,
develops repetitively applied, short duration, control current pulses for
reducing load current pulses through the electrical system. An operator
connects a pair of input contacts across a fuse holder. A circuit between
the input contacts is closed momentarily and repetitively to produce
repetitive current pulses from the electricity source through the system.
A perceptible alert is produced when the magnitude of the current pulse
exceeds that of a prescribed reference current value. In another form, a
tester for an electrical system is designed to plug into the fuse
terminals in a fuse box. The tester can include a plurality of
interchangeable circuit breaker modules to allow the tester to be used on
circuits having differing current ratings.