Discharged batteries are a common issue for technicians to deal with. According to Purkeys Sales and Service Engineer Larry Rambeaux, discharged batteries could be one of two issues: a defective battery or a parasitic load.

So, how to check for a parasitic load with a multimeter? Whenever starting, technicians need to make sure to disconnect all ground cables. Next, use a clip on ammeter to check the load. Multimeters come with a 10amp fuse, so if the load exceeds that it will blow the internal fuse. It is important to check the load with a clip on ammeter first, to ensure the load isn’t over 10amps.

A clip on ammeter isn’t as exact as a multimeter. So once the ammeter determines the load is under 10 amps, connect the multimeter in line with the ground cable. The multimeter will show a more accurate reading of the parasitic load.

Parasitic loads may seem small but they can turn into problems the longer the vehicle sits on the lot. It is important to know what the parasitic loads are to help determine how long a vehicle can sit before needing a jump start.

Are you dealing with battery issues? Are you looking for advice? We welcome your comments and questions below.

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