What do the letters B and K on the ignition coil mean?

When there are such breakdowns in the operation of the internal combustion engine as the disappearance of a spark or a weak spark, unstable idling, the inability to adjust the idle speed, difficult starting or inability to start the internal combustion engine, dips and jerks when starting off and in motion, etc., then it makes sense to diagnose the performance of the ignition coil . To do this, you may need to know the designations of the letters B and K on the coil.

What do the letters B and K on the ignition coil mean?

Per terminal with + sign or letter B (battery) is powered by the battery, with the letter K switch is connected. The colors of the wires in cars can vary, so it's easiest to track which one goes where.

*Ignition coils may vary in winding resistance.

How to connect the ignition coil correctly?

Regardless of the features of the car, the connection is the same:

• the wire coming from the lock is brown and is connected to the terminal with the “+” sign (letter B);
• the black wire that comes from the mass is connected to "K";
• the third terminal (in the lid) is for the high-voltage wire.

Preparing for verification

To check the ignition coil, you will need an 8 mm ring or open-end wrench, as well as a tester (multimeter or similar device) with an ohmmeter mode.

You can diagnose the ignition coil without removing it from the car:

• remove the negative terminal from the battery;
• disconnect the high-voltage wire from the ignition coil;
• disconnect the wires leading to the two terminals of the coil.

To do this, use an 8 mm wrench to unscrew the nuts securing the wires to the terminals. We disconnect the wires, remembering their position, so as not to confuse them when installing them back.

coil diagnostics

We check the serviceability of the primary winding of the ignition coil.

To do this, we connect one tester probe to the “B” terminal, the second probe to the “K” terminal - the output of the primary winding. We turn on the device in the ohmmeter mode. The resistance of a healthy primary winding of the ignition coil should be close to zero (0,4 - 0,5 ohms). If it is lower, then there is a short circuit, if it is higher, there is an open circuit in the winding.

We check the serviceability of the secondary (high-voltage) winding of the ignition coil.

To do this, we connect one tester probe to the “B” terminal of the ignition coil, and the second probe to the output for the high-voltage wire. We measure the resistance. For a working secondary winding, it should be 4,5 - 5,5 kOhm.

Checking insulation resistance to ground. For such a check, it is necessary that the multimeter has a megohmmeter mode (or a separate megohmmeter is needed) and can measure significant resistance. To do this, we connect one tester probe to the “B” terminal of the ignition coil, and press the second probe to its body. The insulation resistance must be very high - 50 mΩ or more.

If at least one of the three checks shows a malfunction, then the ignition coil should be replaced.