Amperage (Current)

Since a multimeter has a very low resistance when measuring current, caution must be used to prevent damage to the multimeter. Always check the recommendations, listed in the multimeter's owner guide for the maximum current to be tested for. As previously mentioned, most multimeters are protected by a fuse when checking for current. However, not all multimeters are protected, and excessive current will damage a multimeter.

The most common use for measuring current in automotive applications is checking for parasitic current drain. This is the amount of current being drawn by the vehicle with all electrical loads off. The normal parasitic current drain for a Saturn vehicle is less than 10 milliamps (although it can go as high as 14.1 milliamps if the vehicle has the Saturn approved anti-theft system installed). This current drain comes from components that require voltage to sustain a memory circuit such as the clock, radio, powertrain control module, etc. However, when checking for parasitic current drain, always check to see if the customer has installed any non-factory installed items that could require constant voltage such as a cellular phone, anti-theft system, etc.

IMPORTANT: The ignition key must be removed from the cylinder before parasitic load testing. The key reminder circuit is activated by the key cylinder switch when the key is in the ignition cylinder, which adds 20 milliamps of current draw.

In the following section "Parasitic Load Testing," two methods will be explained for testing a vehicle for parasitic loads. One method is with the Saturn Parasitic Load Tester (SA 9130Z) and the other method is with a digital multimeter.