Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Inside Microphone, Function Test
With BOSE sound, and inside microphone -R74- is installed to determine interior noise (AudioPilot). This is switched directly with the amplifier -R12-. If interior noise increases, the amplifer (AudioPilot) automatically increases volume according to a predetermined pattern.
After turning on the radio -R-, the amplifier determines the gauge of the inside microphone voltage supply. If the result is OK, there is no reaction.
In contrast, if no inside microphone is installed, three short tones sound one after another.
In case of short circuit, three individual tones are heard.
Function Test
-- Turn on the radio and tune in a station.
-- Set the volume to approximately "20".
-- Now lightly tap on the inside microphone (front interior light -W1-) several times.
The volume of the station selected on the radio must increase noticeably during the tapping. The procedure is done slowly.
-- Stop tapping.
The volume of the station selected on the radio must decrease noticeably.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.