You will need a multimeter to do the job.
Order of execution
1. Disconnect the wires from the microswitch terminals.
2. We connect the car tester in the crankshaft speed measurement mode (see "Idling - adjustment").
Note: In the absence of a multimeter, the crankshaft speed is controlled by the tachometer on the instrument panel.
3. We connect the positive probe of the voltmeter to the gray wire with a red stripe in the wiring block of the block, and connect the negative probe to "mass".
Note: In the absence of a voltmeter, you can use a lamp (probe). In this case, a change in voltage is signaled by a change in the incandescence of the lamp.
4. We start the engine. At idle, the voltmeter should show a voltage of at least 10 V. Gradually increase the crankshaft speed. For a serviceable unit at a frequency of 1600 rpm (solenoid valve off frequency) the voltage should abruptly drop to 0.5-1.5 V. When the speed decreases to 1200 rpm, the voltmeter should show more than 10 V. At the same time, the electro-pneumatic valve should open. Otherwise, the block is faulty.
5. Turn off the ignition. We replace the defective block.
Replacement
1. Disconnect the wiring block A. Using a Phillips screwdriver, unscrew the two screws and remove the control unit.
2. Installation of the control unit is carried out in the reverse order.