Diagnosing a rear SAM failure for w203 before i fork out!

[dasachmo]

Hi guys, I've had a few issues with the car and thanks to everyones help its sorted so far.

I BELIEVE I have a rear SAM failure but will put the signs and symptoms below if anyone can help.

Firstly , It was raining loads, the car started (slowly) but had a light sensor fault. The next morning it wouldn't start. I removed the SAM and it was wet because water had leaked from the boot.

Opened the boot after some difficulty ( the manual lock was seized and because I removed the SAM I couldn't get back in.) after reconnecting it the following systems work:

Central locking works properly.
I can hear the cd changer spinning up.
Im getting a SRS fault occasionally.
The car doesn't turn over. I can hear a clicking from the engine when I turn the key but it wont start.

At rest the speedo is fully lit. At one click it dims and some of the lights flicker. and when I try and start it makes the clicking noise and it goes black / dark..

The battery voltage is 10v when disconnected but when I connect it to the car at rest its 8v.

Was thinking of getting a new rear SAM but merc say they will only provide the newest version so it will have to be recoded with STAR.

Any mobile mechanics that can help in East London / Ilford area!!!??!

 

[Diesel Benz]

Shouldn't you charge your battery before any other tasks (or purchase a new battery)?

 

[dasachmo]

Battery is a new battery.... Do you think it's because of low charge?

 

[grumpyoldgit]

"At rest the speedo is fully lit. At one click it dims and some of the lights flicker. and when I try and start it makes the clicking noise and it goes black / dark.."

^^^ Symptoms of a flat battery or loose connection.

 

[dasachmo]

I don't think it is.... Because if had flat batteries before and the clicking sound Is coming from the engine bay and it's like it's trying to start but doesn't actually turn over... As opposed to the clicking or whirring from behind the dash.
Also lots of different light flash like my fogs which weren't on.

That being said. Sensible things first... Going to fully charge the battery and connect it up.
When buying a new sam. I pasted my model in eBay. The sam number for a 320 also comas a 180. Is it car specific (different engines) or did they use similar sams in different cars.

My details below.....

2095450701
Hw 3702
Sw 4802
5dk008486-11

 

[Diesel Benz]

Battery is a new battery.... Do you think it's because of low charge?

You said the battery voltage was 8 V, definitely too low, be it a new battery or an old one.

Or did you mean the voltage was 8 V on the batter that got replaced? I did not get that understanding from your description.

If voltage is good now and you can hear a click from the engine bay, check if it is the starter relay (only) or if it is the starter motor solenoid that gives the "click".

 

[dasachmo]

aah, the battery is a 12v battery, When i placed the meter accross the terminals it was 8v

Basically 1 click of the key ( just to turn on the electrics) dims the screen
then 2 clicks where the engine is meant to be ready to start thats when it dims and the lights all flicker.

I've had the battery on charge all day so when its a full 12v i'll stick it back in

The only reason i think its the SAM is because it was soaked when i opened the boot and one plug when i removed it had like a scorch mark - or it could just be dirty.

I'll try and unplug all the SAM wires , clean it and plug it in and try it with a fully charged battery

 

[MikeAMG]

A fully charged battery Is at least 12.5v with a good quality multimeter. If you're only reading12v it's dead flat. See below.

http://www.autobatteries.com/en-us/battery-basics/how-a-battery-works/

 

[grumpyoldgit]

Have you dried the SAM out properly? Gentle heat from a hairdryer is probably best, but not too close as to get it hot. WD40 is a water displacer, so it may help to spray the connections if they appear damp.

If your battery is in good condition, the voltage should be between 12.4 and 12.7 volts. A reading lower than 12.4 volts means that your battery needs to be charged.

P.S. Even new batteries can occasionally be faulty. How long has it been on the car and did it perform ok for some time after being fitted?