How to Check for a Parasitic Draw on a Car Battery in Sunnyvale, TX; Drain Test for Vehicle Batteries

Roadside service professionals often hear vehicle owners complaining about their car’s battery frequently dying, needing replacement early, and constantly calling for a jump. What they may not know is that there may be a parasitic battery drainage occurring inside their vehicle. There are some unknown battery drains that occur in vehicles all of the time. If you are having premature battery drains where you need frequent jump starts or you replace your battery more often than you should, then you should test for parasitic battery drains. Citywide Towing Service will walk you through the steps on how you can check your car’s battery for parasitic drains.

Car Battery Drain Test

What you will need: To test your car battery for parasitic drains you will want to make sure you have safety eye glasses, gloves, and a digital multimeter. When using the multimeter you will want to have one with a 20 amp fuse, and have it set to 200ma for proper readouts.
Step 1. You will want a fully charged battery in order to perform this test. You may need to either charge the battery or if you recently replaced the battery, do your test immediately. Before you begin, make sure all accessories such as phone charges, ipods, and GPS devices are all unplugged. Make sure you have no external power devices attached to your vehicle. This will include charging cables. Additionally, make sure the key is out of the ignition and that all of the lights are off and and doors are shut so there is no amp draw coming from the vehicle.
Step 2. To begin the test, remove the negative battery cable which will be the black cable. This will prevent any accidental power surges that can damage to your multimeter. With the negative battery cable removed from the battery’s terminal, use the multimeter. Start by placing one lead on the cable and the other lead to the battery terminal and hold until the multimeter stops. If the reading on the multimeter is higher than 50ma then there is a parasitic draw coming from your vehicle. If at this point you have a reading that indicates there is a parasitic draw coming from your vehicle you will then want to figure out where it is coming from.
Step 3. With a parasitic draw present one of the easiest methods of determining where it is coming from is by connecting the multimeter to the battery. You can use small plastic clamps to help hold the multimeter in place. Keep the negative cable off of the battery but use the clamps to hold the multimeter lead to the battery terminal and the cable. Note: Connect the red lead to the cable and connect the black lead to the battery terminal. With the multimeter now connected to the battery, you should be able to get a constant read without the need to hold the leads. Next you will want to open the fuse box.

Where are the Fuse Boxes Located in a Car?

One is inside the car near the steering wheel and the other is underneath the hood, typically next to the battery. Begin with the under hood fuse box and pull one fuse out at a time and place it back in. You will want to check the meter after you pull out each fuse to see if the meter drops. If the reading on the meter drops you have found the circuit that is drawing the power, or in other words, the parasite. If none of the under hood fuses is the culprit then you will need to check the inside cabin fuse box. Note: Make sure to disconnect the multimeter from the battery before you open the vehicle’s door as you can damage it and get increased reading. Disconnect the meter, and then open the car door. You will need to disable the car door switch to turn off the light when the door is open. You may need to push in a button on the side of the car door or activate the door latch by using a screw driver. Push the door latch in the closed position. With the car door sensors deactivated, begin testing the fuses inside the cabin. You will need to reconnect the multimeter to the battery. Once you discover the right fuse which is causing the power drain, the fuse boxes should provide a label to which fuse that circuit was connected to. Once you discover the parasitic drain you will need to look for your vehicle’s circuit diagram and look for a common or main lead. You might be surprised to find a simple button such as an interior light switch was left in the on position which can be the cause of all of your trouble.

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Hopefully you can find your parasitic drain in your vehicle, repair or correct the problem, and have a more reliable vehicle. If you find yourself in need of towing or roadside assistance, contact Citywide Towing Service.

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