how to check the generator charging with a multimeter?

The most common digital multimeter is suitable for checking the alternator charging. Even the most inexpensive (usually costing 10-20€) device is accurate enough to measure the voltage of a car.

Here's a little help on which one to choose and how to use it:

1. Which device to choose?

• A regular digital multimeter (the safest choice): it's the square device with a screen and two leads (black and red) attached. It will show you the exact volts (e.g. 14.2v).

• clamp meters: these are the ones with the "jaws" on top. they are also very suitable for measuring voltage (they also have holes for wires on the bottom), plus if necessary they can also measure how much current (amps) the generator is putting out without disconnecting the wire. for the home user this is a "nice-to-have", but a regular multimeter is perfectly sufficient.

What not to take: Don't take a simple "indicator screwdriver" (which only lights up). It only shows that there is power, but doesn't tell you whether it is 12v (battery empty) or 14v (alternator charging). You need numbers .

2. how to measure with a multimeter (wooden and red)

Once you have received the device, do this:

1. wires connected:

   • Put the black wire in the hole marked com .

   • Put the red wire in the hole marked with a v (often vωma).

2. set:

   • Turn the dial to dcv or v= (there is a straight line and a dashed line next to the letter v). This means direct current.

   • If the device has numbers, select 20. (This means the scale is up to 20 volts, which is ideal for a car's 12v system).

3. measure (engine stopped):

   • Place the red tip on the positive (+) terminal of the battery.

   • Place the black tip on the negative (-) terminal of the battery.

   • The display should read approximately 12.3v – 12.7v .

4. measure (engine running):

   • Start the car.

   • keep the tips on the terminals the same way.

   • Now the number should increase. With a good alternator, it will be between 13.8v – 14.5v .

Interpretation of results:

• below 13.5v: the generator is "tired" or charging weakly (check the belt and connections).

• above 14.8v: the voltage regulator is faulty and "boils" the battery (dangerous for electronics!).

• stays at 12v (does not change when starting): the generator is not charging at all.