I also put an EBay link on one of those threads, for an Ammeter that plugs into the Fuse holders, cost about £10, or you can just make up some short leads with "filed down" male spade crimps, and use a regular digital multi-meter
One of the posts I was referring to is actually, (currently), 3 posts down from this one,
Thanks Dave!! When I wrote my first post I was going to put in links of all the relevant posts and threads I had read. By that time I had already monitored the current drain for two nights and two days straight. What I was trying to find out was which component was causing the drain and what was the fault with it. Given that it is a ring and the circuit is complex, I knew that the Audio Gateway was the reason for the drain. What I wanted to know was whether the drain caused by Audio Gateway was the consequence of some other component failing or the fault lay in the Audio Gateway itself. Since the radio worked just find, I suspected my Audio Gateway was not faulty.
Over the weekend, I went and spoke to technician at the dealership. I spoke to my own mechanic. I also tried to speak to another reputed Indy shop, but it was closed. I am not a DIY person, other than for very small things. I must have spent about 12-14 hours reading all I could on this and other Mercedes forums over last week. Everyone and everything seemed to suggest that either I change the Audio Gateway or it would take a lot of time for someone to find where in the circuit the fault may be (CAN Bus, SAM, Audio Components, the wires, etc). It could have been anywhere.
I bought fuses, fuse taps, inline fuse, replays, preparing to hack the circuit to power the Audio Gateway through switch-on fuse slot. I couldn't find any easy tool in the market which would allow me to connect power
side of "switch-on" fuse to the load
side of "always-on"/"constant" fuse. My idea was to insert an in-line fuse between the power side of "switch-on" fuse (which only gets power when the key is turned to ACC or engine is running) to the load side of the fuse location of Audio Gateway (the load side connects to Audio gateway). [If anyone tries this method in case your Audio Gateway doesn't go to sleep, you will have to remove the Audio gateway fuse and find another power source in the fuse box that is powered by ACC or engine being turned on or off. Then connect that power source to the load side of the Audio Gateway's fuse holder. Make sure you have an equivalent fuse inserted inline. Don't attempt this if you don't know how the electric circuits work, how the current flows and what voltage is!
]. Is there any single leg fuse connector - that will make it easier to splice the either end of the in-line fuse wire to power and load connectors of the respective fuse holders. Other option was to tap into the relay for power source or insert a relay to power via "switch-on" fuse to the Audio Gateway load side. Some other posters have written about the latter two options of using the relays.
I spoke to everyone about the problem with steering wheel control buttons and my doubts that the short or something in it may be causing all these other symptoms. My only reason for doing so was that the things started happening after my steering buttons started malfunctioning. Yesterday (Sunday), I decided I will open up the steering wheel myself and see what's going on with the connections between the buttons and whatever PCB may be there. I purchased a soldering iron assuming there may be a loose connection.
After opening and disassembling the steering control buttons, there is a PCB on the each side. There was corrosion on one of the PCBs. I used my trusted Deoxit, which I had bought a few years back for my home audio equipment. Deoxit can clean the deposits of connectors and PCB. It also helps improve conductivity. After cleaning the PCBs and connectors, I had my steering control buttons working normally.
It also caused the battery drain issue to go away (fingers crossed).
I have been monitoring the battery drain for past 16 hours and it is close to 20 milliamps (plus minus 10). My battery voltage after 15 hours was 12.47VDC. I have posted a few pictures below. When I have time I will post a more detailed post of all the links that helped me as well as more pictures and videos (will need to edit)
. I also used go-gone and the soap water to bring my buttons to pristine conditions.
Apparently the problem seems to be solved. I don't have the wiring diagram but the cleaning up contacts and allowing circuit to function as it was originally supposed is now allowing the Audio Gateway to go to sleep. It also solved a completely unrelated problem of dimming mirrors. Now only thing I need to take care of is the Teleaid/SOS malfunction and SRS warning messages that come when I turn on the car. They were there before too and I read up plenty about that during last week as well. I will probably try to contact an Indy to see if they can help (the dealership service guy quoted $210 just for the diagnosis of why the message is coming up or before he will disable it!)