How to use a multimeter on a car

Equipped with electrical add-ons, car models today need a thorough checking now and then. Test lamps are used to check electrical circuits when attached to live wires and the ground. However, it is only capable of detecting a supply of electricity at the particular area of interest. It makes more send to use a testing device to check how much voltage is being drawn by a specific component as well as determining the resistance of an electrical circuit.

Multimeters as measuring devices

Multimeters are designed to measure different electrical properties. You can learn how to use multimeter on a car fuse, on stereos, wipers, and heated areas of your vehicle. They have functions that will benefit vehicles since cars also have electrical components as well. Multimeters check the direct current of DC. Multimeters also read resistance, the current, and voltage. Some multimeters may come with features for measuring the engine’s speed and angle. During every test, it’s essential to properly connect the probes to the respective ports to avoid the risk of blowing up the device. As a safety measure before every test, remember to always put the meter to zero especially when low resistances are measured. It is safer to use a digital multimeter than a needle meter because it has a higher risk of overloading and getting damaged.

Using the multimeter

Connect the meter to the posts to check battery voltage. At the HT circuit, you can test for the resistance by touching the test leads. With the meter connected to the shunt wire, you can record the output of the alternator.

Record alternator or dynamo current output using a meter connected to a shunt wire. Test voltage to the coil or any other circuit by comparing one side of the meter to the channel and the other side of the earth.

How To Take A Reading


You must make sure that the test leads must be connected the right way and the polarity of the card has a significant influence on this. Cars that make use of the negative earth system should be using the negative lead. It’s the same case with cars that make use of the positive-earth system that needs the positive test lead. Your car manual will be able to tell you its polarity. Check for rusting or paint residual in the area of contact and clean them with a paper towel to avoid getting the wrong reading. The battery is better connected to the earth terminal when working on the engine.


Checking the battery

The battery must be first checked to make sure that its performance stays efficient.

  • Connect the leads to the battery terminals after setting to the correct scale of 0-20V. Depending on the charging state of the battery, the reading of 11 volts should suffice at low charging and 12 volts for a full charge.
  • A faulty battery cell might be in your presence if both tested lower than 10V. Relocate the earth lead anywhere in the body of your car then perform another reading for the voltage once more. Ideally, the meter reading should yield the same as the first one. If it’s lower, there could only be a weak contact from the earth lead to the battery terminal. Redo the procedure as you connect the earth-lead to just one of the meter leads while the other links to the live terminal of the battery and starter solenoid.
  • Correct the low readings found before moving on from the battery leads to the other electrical circuits of your car. Make sure to maintain the connections and retest the voltages properly. After making sure that the tests all led to the same results, keep the reading for future reference for the other circuits.

Check the sender unit

The gasoline tank makes use of a resistor. You can use the multimeter to measure its resistance. Detach the wire leading to the sender unit then connect the appropriate earth point to the meter and the terminal. The reading should be ready if the sending unit circuit has completed. A full check of each interpretation with an empty tank, a half-full tank, and with a full tank.

As the readings progress, there should be lesser gaps, or equal ideally, among them. However, there could be a sign of shorting out with the resistor tracks if two of the readings had turned out very close. It could well mean a false reading.