greg121121

Hi. I have a C5 coupe that has really low volume. All fuses are good, and when I remove the Bose relay, the volume returns to normal levels but has no bass. I've tried swapping the head unit out for a known good one and still have the same problem. What are common causes of this? Thanks.

Rob 02

You may have a problem with the Bose signal processor located in the drivers side foot-well near the gas pedal. It is also possible that one of the connections to it are bad.

The stereos low level signal goes to the processor then is returned to the head unit for amplification. After amplification the High level output goes directly to the four speakers. Another line from the processor goes to the woofer amplifiers in the doors.

I just looked at the schematic in the factory service manual. It's my guess that disconnecting the Bose relay takes the processor out of the equation, allowing full unprocessed speaker output to go directly to the four speakers but without low level from the processor to the woofer amps.

You have already eliminated the other components as a possible cause.

If you buy a processor on eBay they will usually refer to it as a Bose amp. It's not really an amp.

I hope this makes since?