27
ATTENTION:
All instructions in this troubleshooting refer to the entire sound system and its individual com-
ponents. The features of your device may not match the functions described in the notes. Then skip this point
and move on to the next one.
Amplifier moduleS ACTIVATES THE PROTECTIVE CIRCUIT / THE PROTECT LED ILLUMINATES
Check the following steps:
Short circuit on the speaker cables
• First disconnect all speaker cables from the amplifier module. Use a multimeter to check the ohmic impedance
of each loudspeaker by measuring between its plus and minus lines. With standard loudspeakers the value
fluctuates between 3 and 5 ohms. The values for low-resistance subwoofers can be lower.
• The measurement shows a resistance value of less than 0.5 Ohms
Then there is a short circuit. Remove the wiring of the affected loudspeaker at its connections. Now use the
multimeter to check the ohmic impedance directly at the loudspeaker connections by measuring between
the plus and minus connections.
The measurement shows a resistance value of more than 0.5 Ohms
• The speaker is fine, so the speaker wire appears to be defective and causing a short circuit.
Replace the defective speaker cable.
The measurement shows a resistance value of less than 0.5 Ohms
• The speaker appears to be defective and is shorting out. Replace the defective speaker.
The load impedance of the loudspeakers or the subwoofer is too low
• Compare the ohmic impedance of the connected loudspeaker or subwoofer with the technical specifications
of the amplifier module. For example, if the amplifier module is only designed for 2 or 4 ohm operation, no
loudspeaker with less than 2 ohms may be connected.
The cross-section of the power cables is too small
• If the cable cross-section is too small, this leads to an increased ohmic resistance and thus to a voltage drop
(voltage loss). This indicates that the amplifier module consumes more power. The increased power consump-
tion results in a significantly higher heat development and the amplifier module switches to thermal protection
mode. Therefore, observe the recommended cable cross-sections in these instructions and, if necessary, lay
power cables with a larger cable cross-section.
The amplifier module is overheated (refer also to page 17)
The heat sink of each amplifier module requires sufficient air circulation to be able to dissipate the heat generated
during operation. If necessary, change the installation position in favor of better cooling of the amplifier module or
ensure better air circulation at the installation location.
• Turn off the sound system and wait about half an hour for the amplifier module to cool down again. With very
hot outside temperatures and strong sunlight, enormous heat develops inside the vehicle. The amplifier module
then activates its thermal protection circuit to prevent damage. After cooling down, the amplifier module works
properly again.
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