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· Registered
2008 ML320 CDI - Arbonne Incentive
30 Posts
Discussion Starter · #1 ·
So I am swapping out the stock COMAND for an AVIN unit and have located what is supposed to be the proper switched power/ground leads for the CAN BUS and head unit and find that it is always ON. I know that this was not always the case as the original radio did at one time shut off with the ignition switch but has not done so prior to the swap.

In testing these power lines, I sparked something and now there is NO power on this line at all - ever.

Is there a relay/fuse for this? I looked at those under the engine compartment, on the drivers side dash, and the drivers side rear and could not identify any blown. Is there a fuse or relay in the electronic ignition switch? An issue there would help explain the prior issue of the switched power being always on.

If its in the EIS, is is best to locate another switched source? Or how easy is it to repair? I can see that its fairly easy to remove. Or where is the best place to locate a switched power source of sufficient power for the AVIV and CAN? Everything else seems to operate as normal.

Vehicle is W164 2008 ML320 CDI

· Coupe/Convertible Forums Moderator
CURRENT: 2011 SL550 FORMER: C300, ML350, CLK550 Cabriolet, C240, ML320, 300TD
25,449 Posts
First of all, there is NO switched power source on the radio wiring. There is only constant 12v. Turning the factory radio on and off with the ignition switch (and activating illumination with the headlights) is controlled via CAN bus signals.

For aftermarket radio, you might try tapping into the cigarette lighter for switched 12v and illuminations.

There is a fus for the radio. Here' the fuse chart:

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