MB-Dude

In my '96 SL600, the standard MB factory Bose radio is supposed to change volume as the speed of the vehicle changes - increasing speed should produce increased volume. My volume remains constant regardless of roadster speed. The radio/headunit has been changed and the problem still exists. I also know there is a wire that sends a signal to the radio/headunit indicating vehicle speed, but I do not which it is.

Question #1 - Can someone tell me which wire going into the back of the radio/headunit is from the speed sensor? If I know the wire, I can monitor it for a signal while driving.

Question #2 - Can someone provide the circuitry and/or component(s) that create the vehicle speed signal? I suspect the speed sensor has failed.

bobterry99

The speed signal comes from the instrument cluster and goes to the climate control unit and the radio. It is a green wire with black stripe. The simplest way to check the signal would be to monitor it through climate control diagnostics. See test #18 here: http://www.benzworld.org/forums/r129...ml#post1879667.

MB-Dude

Thanks! I'll check it out this weekend. (Instrument cluster, eh? Could be a big financial 'ouch'.)

bobterry99

The link I posted above is for '97 and later R129s. For earlier cars see this link: http://www.mercedesshop.com/shopforu...ad.php?t=86546.

MB-Dude

Thanks for the more applicable instructions!