Current Load Testers

Current load testers are a handy piece of kit when your got electrical problems.

There are two of them in the pic above, the larger of the two is good to 80 amps @ 48 volts DC. It has adapters for maxi, standard and mini blade fuses. It also features both hold and peak settings.

The smaller one is only good for 20 amps and doesn't have the adapters or the setting of the other.

You'll also notice a blade fuse holder with orange wires, this is something I knocked up so they could be used in applications that don't have blade type fuses.

You can use them for a "No Load" test, this is where you can find a parasitic drain on the battery, if you get a reading without anything on that fused circuit being on, it indicates a current drain.
Note: Some circuits always have something on draining current such as the clock, alarm etc.

Note: the probe of the tester plugged in place of the radiator fan fuse.
The is a slight drain of .03amps on this circuit.

Then there is the "Peak Load" test.
You set the tester to "Peak" and turn on whatever is on that circuit. In this case the radiator fan has cut in and is showing a peak loading of 14.8 amps.

Given that the radiator fan circuit is protected by a 15 amp fuse, this reading is excessive. Peak loadings occur when something like an electric motor switches on. It's normal for electric motors and some other equipment to use more power on start up than normal running, but excessive current usage indicates trouble.

Finally there is the "Constant Load" test. You set the tester to normal and observe the reading whilst the circuit is in normal use, such as the lights are on or the electric motor is running normally.

Here the fan motor is using 5.2 amps constant load in normal running.
Yet again it's a bit excessive, as most other times it was using only @ 2.2 amps, and as little as 1.8 amps.

There are other instruments for testing current loadings and we'll look at them sometime in the future.