Monotronic
This part combines a switch and a powerful transistor ignition final stage with an ignition coil: combining in one housing prevents voltage losses.
To supply the voltage of the primary winding to the part of the ignition coil, a black wire is used from the mounting block to the ignition transformer. Via terminal contact (15) connection is made to the primary winding at the so-called closing time
To ensure that the necessary ignition energy is available in the entire area of work, the time for applying current to the ignition coil part is selected according to the number of revolutions and the supply voltage. In addition, switching (commuting) the part can limit the primary current to the ignition coil part to a maximum value.
To protect part of the ignition coil, the ignition transformer has a safety shutdown system. Since the current circuit is always closed when the ignition is turned on, the coil windings can overheat when the ignition is left on for a long time. This is prevented by safe disconnection: to the terminal (15) 12 V is applied, and on the terminal (1) on the contrary, maximum 10 V (or less). Thus, in the winding «consumed» at least 2 V, which can cause them to overheat. However, already after 1-2 seconds, the ignition transformer approaches the terminal (1) also 12 V. There will no longer be a voltage difference in the windings and the consumer is switched off in a peculiar way.
The interrupt pulse is fed through the ignition/injection control unit via the green/black wire to the switching part with the final stage of the ignition transformer. There, the pulse of the Hall sensor is processed and amplified, which, as indicated above, controls the current through the primary winding via the contact of terminal 1.
High voltage, about 35000 V comes out of the thick terminal (4) transformer and passes through the high-voltage wire of the distributor cap.
The brown wire connects to «weight».
Checking the ignition transformer
The illustrations show how to connect the instruments for testing the ignition transformer.
The visual check is described above.
To check the resistance, remove the three-prong plug and the high-voltage wire at the transformer with the ignition off. The primary and secondary windings of the ignition coil part are measured.
Using an ohmmeter, measure the resistance between the transformer terminals 1/- and 15/+.
Rated value: 0.5-0.7 ohm.
Carry out the next measurement between the terminals (15) And (4).
Rated value 3-4 kOhm.
If the measured values do not match the specified values, replace the transformer.
With these measurements, a short circuit between the windings cannot be recognized. If, nevertheless, suspicion falls on the transformer, despite satisfactory measurement results, then the removed transformer must be checked in the workshop.
To check the voltage, you need a voltmeter with wires with sharp tips.
Connect a voltmeter to the external contacts of the three-prong plug of the ignition transformer.
Turn on the ignition: the voltmeter should show about 12 V. If there is no voltage. then you need to look for a break in the positive or «mass» wires.
Switch off the ignition.
Using auxiliary wires with sharp tips, connect the LED voltage probe to the contacts (2) And (3) ignition transformer plug.
Have an assistant turn on the starter.
The LED should flash. If this is not the case, then either the Hall sensor or the control unit is faulty.
Switch off the ignition.
Safe shutdown: put the 3-pin plug back on the transformer.
Connect a voltmeter to the terminal contacts (1) And (15) transformer.
Turn on the ignition. Voltage must be at least 2V (voltage difference between windings).
After 1-2 seconds, the voltage drops to zero.
If this is not the case, then the safety shutdown of the transformer is not working properly and the system must be replaced.
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