On cars, two sound signals are installed; one (C305) tall with trumpet (C304) low tone. Sound signals are placed in the engine compartment and mounted on a bracket attached to the left radiator shield.
Signals C304 and C305 are electromagnetic, noise type, creating a sound of a fairly wide frequency range. The main frequency of sounding a low tone signal is 405-445 Hz, and a high tone is 470-495 Hz. The high and low tone signals differ only in the thickness of the membrane: the C304 signal has a thicker membrane than the C305 signal. The current drawn by each signal is 4A. Therefore, they are switched on without auxiliary relays directly by a switch located on the steering wheel.
Causes of malfunctioning audio signals may be as follows; the switch does not work or sticks, or the sound signal itself is faulty. To detect a malfunction, check the reliability of the wire connection, the condition of the switch contacts. Clean contacts if necessary. A defective switch or horn is replaced with a new one.
If the volume of the sound of the signal decreases or wheezing appears, adjust the signal. To do this, the second signal is turned off and by turning the adjusting screw on the signal housing in one direction or another, a loud and clear sound is obtained. If the adjustment does not eliminate wheezing or if the signal is intermittent, then it is disassembled and the contacts of the breaker inside the signal are cleaned. When assembling the signal, it is necessary to install the previous gasket between the membrane and its body so as not to disturb the gap (0,4±0,05) mm between core and armature.