What Is The Normal Parasitic Load On An Automotive Electrical System?

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When it comes to maintaining our cars, we often focus on the engine, tires, and brakes. However, the electrical system is equally important and can cause significant problems if not properly maintained. One of the key factors to consider is the parasitic load on the system. In this article, we will discuss what parasitic load is and what is considered normal for a car’s electrical system.

What is Parasitic Load?

Parasitic load is the amount of power that is consumed by electrical components in a car when the engine is turned off. This load is typically caused by devices such as alarms, clocks, and electronic control modules. While these devices may not require a significant amount of power individually, when combined, they can add up to a substantial drain on the battery.

How is Parasitic Load Measured?

To measure parasitic load, a technician will use a multimeter to measure the electrical current that is flowing through the system. The current is measured in amps, and a normal parasitic load is typically between 25 and 50 milliamps. If the load exceeds this range, it may indicate a problem with the electrical system that needs to be addressed.

What Causes High Parasitic Load?

There are several reasons why a car’s electrical system may have a high parasitic load. One common cause is a faulty electrical component, such as a malfunctioning alarm or radio. Another possible cause is a short circuit in the wiring, which can cause excessive current flow and drain the battery.

What are the Effects of High Parasitic Load?

If the parasitic load on a car’s electrical system is too high, it can cause several problems. The most obvious is a dead battery, which can leave you stranded and require a jump start or replacement. Additionally, high parasitic load can reduce the lifespan of the battery and other electrical components, leading to costly repairs down the line.

How to Reduce Parasitic Load

There are several steps you can take to reduce the parasitic load on your car’s electrical system. One of the simplest is to disconnect any devices that are not necessary, such as an aftermarket alarm or stereo system. You can also invest in a battery disconnect switch, which will cut power to the entire electrical system when the car is not in use.


In conclusion, understanding the normal parasitic load on your car’s electrical system is important for maintaining its overall health and preventing costly repairs. By monitoring the load and taking steps to reduce it, you can ensure that your car is running smoothly and reliably for years to come.

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