Parasitic Draw Test - How to Test for Amp Draw

Parasitic draw test is a simple test to know current amp draw from your battery, huge amp draw is enough to drain the car battery overnight.

How to test amp draw that causing overnight drains on the car battery? Current draw or parasitic draw is the continuous drawing of power from your car battery even if the engine is turned off, this draw will discharge your battery faster than normal.

Parasitic Draw Test with multimeter

1. Conduct the test on the negative side by removing the battery cable from the negative battery terminal. Set the multimeter to the current measurement setting. Make sure that the engine is turned OFF.

2. Connect the multimeter in series with the battery to complete the circuit. The negative test probe of the tester to the negative battery cable then the positive probe of the tester to the positive battery terminal as shown in the illustration.

3. Read the measurement indicated on the multimeter, if the reading is zero there is no draw, if the reading is greater than zero (Ampere > 0) then there is a current draw. A draw of 2.0 A is enough to cause the battery to drain overnight.

How to identify the circuit causing parasitic draw

First, locate the fuse box, one fuse box is located in the engine compartment, usually near the battery. The other fuse box is located inside the cabin, usually, it is located on the driver's side underneath the steering wheel.

Set the multimeter to DC voltage measurement setting then measure the voltage across every fuse as shown in the illustration.

Record the measurement reading, makesure to measure the voltage across all fuses (fuse located on the engine compartment and fuse located on the passenger cabin). Makesure all the electrical equipment and accessories is turned off.

If the measurement is,

0 – The circuit is OK and there is no draw.

OL – The circuit is OPEN, check for the busted fuse.

Greater than zero (0) – This is the circuit that draws current from the battery, check if there is a load that functions which causes draw.

Using Multi Tester to Complete the Circuit of Alternator

Remove the B+ terminal of the alternator. Make sure that the engine is turned OFF. Observe the reading on the ammeter, if the reading is zero then the circuit is okay or the Alternator is Okay if the reading is more than zero the diodes on the alternator are shorted.

How to Test an Alternator with A Multimeter

How to test an alternator with a multimeter can be easy if you just know the proper way to do it. Just follow the simple procedure mentioned. Read more » How to Test an Alternator

How to Disconnect a Car Battery

Do you know how to disconnect a car battery? as simple as it is, not doing it correctly increases the possibility of damaging your car's electricals. Read more » How to Disconnect a Car Battery

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