sdr198

Hi all,
My ML420 CDI's dashboard lights don't want to go off....

When I turn on the car, they all come on, stay on when I drive off and don't turn off when I switch off and lock the doors.

Another thing I noticed is that, when I turn on the headlights and forget to switch them off before leaving the car, there's a loud bell sound (or beep) that won't stop even if I turn off the headlights...

I changed one of the parking sensors recently so I'm worried this may be causing these issues...Checked the OBD error codes but nothing came up... Any help would be great as I'm worried the battery will die soon if I don't fix it (I'm having to disconnect the battery to stop the beeping and the lights).

Thanks in advance!

Plutoe

It's not an OBD fault and that is why an OBD reader is useless for body and chassis faults--------------in any event check\test the front SAM!!

sdr198

Thanks Plutoe for the prompt reply. I had a look at the front SAM. There doesn't seem to be any water ingress but.... someone's definitely touched it before as it was missing the screw that fixes it to the unit! I tried to move it and noticed that some of the lights went off when I did so.. I haven't done a full test though.. how do you do that? I'm not sure what tools I should use.. STAR?

Plutoe

Regrettably the SAM have many microprocessors as apart of the unit and you need factory or equal diagnostic equipment to solve and define the fault.

sdr198

Apparently (as reported by the experts), there was a reverse voltage on the board which resulted in a number of diodes shorting, thus causing the lights to stay on all the time.... They should have fixed this by the end of the day today... probably cost around £300 instead of £950 for a new instrument cluster.