ACRB

Hi Guys…. Just bought a low mile (30K) 2007 S550. Love the car, and it’s a pleasant change over the 997. Several minor concerns that I hope the Forum can help me with.

• Night vision doesn’t work.
• Clock wont synchronize with computer (Even though clock runs) also doesn’t illuminate at night.
• Small switches on side of display don’t function. (Screen tilt or brightness).
• Front cigarette lighter not illuminated, or working.

Wondering if it could be a fuse or relay? Any input GREATLY appreciated.

Mike5215

In the trunk under the floor panel is the spare tire well. In the well should be a folded document that has the fuse diagrams for the car. You'll need to hunt down any that might be related to the issues and verify they're not blown. An indie or the dealer may also be able to pull fault codes that would put you on the right track.

ACRB

Great..... thank you. So, does it sound like a fuse issue? I guess because of the close proximity of everything, it must be related.

Mike5215

I've never heard of that specific constellation of symptoms but all of that gear is in very close proximity. It's possible they're on the same circuit. That would be the easiest place to start.

greglig

Hi have a look at the diagrams in this post. There are three items on one "lin bus" (this is a type of single wire network). If the clock is working but the switch assembly next to the display is not it's not likely to be a fuse.
Before you or the dealer replaces anything I would recommend disconnecting both batteries and wait 5 min's. Must be done in order: negative terminal on front starter battery first then the consumer battery behind the rear seat, look for other posts on this forum for how to get access.
Then reconnect and see if it all goes back to normal. You will most likely need a dealer or reputable workshop to clear error codes after doing this. Car will run and drive fine but you may get warning errors on the cluster.

The only reason I say to do this I diagnosed a 07 S500 (when I was in Australia) with a very similar problem but it seemed to be only the headlight switch, in all honesty did not check any of the other items on the bus. Used a scope to check for bus activity which showed none. Then disasembled switch and check for 5v to the micro and xtal activity which were both normal.
Car went to Mercedes to be fitted with new switch (AUD$1000). The dealer rings up and say they cannot program the new switch!! what gives?? I didnt think they can be programmed but I could be wrong. They could have ment the UCP (upper control panel - A/C controls in the center of the dash).
Attempted many times with no success, as a last ditch effort they reset everything by disconnected the battery and all of a sudden it worked ok.
Turns out the old switch was fine too but something was stopping communication on the bus. One of the modules had locked up and causing the error.

If after doing the battery reset and things are still the same I would recommend disconnecting each module in turn and see if things start working. Could be a dead network transceiver chip in one of them.
If you need help on how to remove things just ask.
Failing that you will need to have error codes read.


Hope this helps
I'll look up the diagram for the front cigarette lighted in the next post.
Cheers.

greglig

Front Cigarrette lighter diagram: Component "R3". Goes to front SAM, out in the engine bay next to the brake boosted.
Please what ever you do if the fuse repeatedly blows don't just keep going to a bigger and bigger one.

I know that sounds silly but the amount of times I seen mechanics do that it astounding. Then they complain when I tell them sorry you module cannot be repaired they are all upset.

Just a side note: when the cigarette lights bulb is blown you will not have park brake switch night time illumination also. If you turn on the headlight switch and you see the park brake switch flash three times and then go out. It will only do this once per ignition cycle.

On my car it took me a while to work out whats was going on as the error code the front sam was giving me was somewhat misleading. When you click on the error code it tells you what functions are impaired then everything was clear.
Mercedes Star Scanner (Xentry Diagnostics) Best Scanner system I have ever used and I've used just about all of them.

To get to the cigarrette lighter just open the comparment next to it and remove the two rubber bumpers, then remove the two torx screws and gently pull the storage compartment up and out. The lighted assembly just comes forward. Also the plus disconnects sideways and can be a but stuck. Be gentle to to damage it.

By the way not sure how the uploaded images appear in other peoples browser but if your on a normal computer use the centre button to click on the image to give you a new tab and a full size image instead of the java popup.

Cheers.

Zerocarpileup

Change the clock out. Trust me. I bet your headlights only work on auto also. You can't even turn on the fogs either. Don't know about your night vision but I had the same issue before. I changed out the light switch, nothing. Changed out the buttons on side of screen, nothing. It was the clock all along. All tied in through the clock.

ACRB

Guys, thanks for the exceptional response.......greatly appreciated!