We have a 2005 ml500 that has been having strange electrical issues which seem to be getting worse...it started with the cluster...all gauge needles sputter and drop to zero then back to normal for about 5 minutes every time we drive the vehicle...now the nav will not complete a destination and as of yesterday the cd does not work...also the cabin and headlights flash when the gauges lose power....we have a bumper to bumper extended warranty with only 700 remaining before expiration...we have had it at our local mechanic and to Mercedes where they spent almost 6 hours diagnosing/troubleshooting....there is nothing to "see" which seems to be exactly the problem...I see Michael answered a somewhat similar question so we are hoping someone here is familiar with this specific issue....the local mechanic sent out the cluster for bench testing and the problem could not be recreated but when it is reconnected to the car it happens and has gotten more frequent in the past month...I am more than happy to send you a video of the gauges sputtering and dropping to zero as we are driving down the interstate...we provided it to the warranty company which is why they have agreed to fix it...however, the cluster itself does not seem to be the problem since it works fine when NOT connected to the vehicle...local mechanic called it a communication error....Mercedes mechanic just shrugged his shoulders and said we can replace the cluster but has no real confidence this will fix the problem...as the cluster problem worsened the nav began to act strange and, as I mentioned the cd changer now will not function since we left the diagnostic marathon appointment at the dealership....could it be a SAM failure or the AGW?....this is profoundly important because if the problem is not fixed we are done...our warranty is over and we cannot afford the expense of fixing it when we finally experience a catastrophic failure which, with the mounting electrical anomalies seems inevitable....this is our ONLY vehicle for a family of 5....please help

 

There are no SAM modules in a 2005 ML.

Please UPDATE YOUR PROFILE in USER CP.

 

got it...clearly I am clueless...could it be the extended activity module causing all three problems?

 

Please include the year (2005) in your profile.

The first thing that you must do is check the GROUND for the Instrument Cluster and the radio which is located at the right side kick panel.

Remove all the cables and check for corrosion and replace in the same configuration.

 

checked....nothing looks bad...also checked by the Mercedes tech (almost 4 hours of diagnostics and no bad wiring found)

 

Do you have the veh. in your possession or is it at the dealer or repair shop?

Did you ever have water enter the right side front passenger footwell?

 

the vehicle is here...absolutely no water leaking..nor evidence of a previous leak...we have had the car for almost two years with no issues...in the last 6 months the instrument cluster failure has become progressively worse...today the needles twitched and dropped to zero no less than 25 times while driving...cluster lights flash and overhead trip computer and interior lights visibly get dim and brighten while the cluster is acting up....do you think it could be the extended activity module failing as suggested or could a bad cluster be causing all of the problems (the cluster was removed and sent out for bench testing and did not fail once during the 3 day bench test)

 

I have no idea how they bench tested it, but if they did it the correctly then it must be a GROUND problem, because they use a ground that is not from the vehicle.

 

ground in passenger foot well and ground near firewall at the battery....mercedes tech and I checked and no problem...could it be the EAM?

 

If the problem lies anywhere it will be with the AAM. But you will have to make the call.

Remove the two plastic covers to the underhood fuse relay box, then remove the three additional screws and pull the module out of the box.

The AAM will be attached to the fuse box. Find the tag attached to it and cop down the four numbers, e.g. 163 545 xx xx.

Post back with the info.

 

may have discovered the problem....rear tail light cracked and standing water inside the light on left (side marker lamp) and right bulb is blown...fuse is not blown...could data faulty data be sent from this short ...could this be causing all the problems?

 

I don't think so, but you can never tell.