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Old 03-14-2011, 12:54 PM
gahawkins gahawkins is offline
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Location: Rochester, NY 14506
 
Join Date: Jul 2009
Posts: 20
Mein Auto: 1991 M5
If it's a BMW radio (the non M E34 series will be the same) then I would start with the amp for the speakers, which is located in the left (drivers) side of the trunk. Remove the mat on the left trunk fender wall. A couple a screws and it will be lying on the trunk floor and can be examined easily. All the radio outputs for front, back, left and right channels come from the radio to this amp and the speakers all connect to this amp. I can probably find the wiring diagram for you, if you come to this stage and need it. There are two removeable multi-pin connectors; don't hesitate to remove them. Each pin is numbered and the wires are color coded. Once removed, you can use a pair of airline headphones to test whether any music is coming from the radio to the connector pins. You should have something like four channels of radio sound. Even if one doesn't work, you would have speaker sound from the others. If there is sound on at least one or two feeds from the radio, and no sound to the speakers, the amp is probably not "turned on." This requires not only 12 volts from thebattery supply, which is always present on one of the connector pins, but also 12 volts on another pin which is sent from the radio when the radio is turned on. That signal activates a relay in the amp that connects the amp to its battery supply. Nothing like complexity. If the radio fails to provide that signal when it is turned on, the amp will appear to be dead.
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