pg043

I bought a 2007 C230 at auction a couple weeks ago. The battery was dead before the auction started and it was jump started with a spare car battery--I have read that that can fry the rear SAM.

There are a collection of issues I'm having, and it sounds like they are all related to a faulty rear SAM module.

1. The right rear turn signal doesn't come on.
2. The left rear turn signal will come on, but if I leave it blinking, it will fizz out and stop working. If I turn the signal off, wait 5 minutes, and try again, it usually comes on again but then fizzes out again.
3. One of the brake lights works, one doesn't.
4. The remote unlock on my key fob only works about 20% of the time i press the button. Usually I have to stand right next to the driver side door to get it to unlock.
5. My windshield wiper speed settings are crazy. The third setting is slower than the second, and they will randomly change speeds without me changing the setting.
***
6. I don't think this is rear SAM related, but I have a "break wear" indicator light on at all times. My car only has one brake wear sensor, on the front passenger side wheel. The pad has 80% and I just replaced the wear sensor but the light is still on.


If I am correct and the rear SAM does need to be replaced, I would like to do it myself. I guess I'd try to get a used one from eBay or a pull a part type place. Can anyone tell me the part number? And if I do replace it, will I still have to bring it to dealer to have it reprogrammed?

Thanks!

Holmes5518

Personally, If I were you I wouldn't start throwing parts at it. Take it to a dealer and pay an hour diag fee to find out what it is. You'll save money in the long run.

pg043

Yes that's good advice of course. I just want to have as good of an idea as I can of what the problem might be and how I can fix it so I have a game plan before I take it to the dealership.

Moviela

All of the problems you report can be caused by a flat battery. If the battery is not a genuine Benz or one of the very expensive aftermarket silver calcium batteries, that will contribute to a low bus voltage problem.

Not all of your problems are rear SAM related. Heed the advice to have a star machine and a good technician diagnose the causes. A word of caution on a used SAM. It might need version coding to fit your car and options. It can be tough to find anybody that can change the coding for your car. While not much cheaper than a new SAM, there are companies than can repair your SAM.

For your key, replace the batteries with fresh name brand coin cells. If you have tint on the rear window, that might be your range problem. The receiver antenna is the warming grid on the window. If the stripes don't get warm, you need to complete the circuit of the grid.

Your brake wear sensor must have the wires laid exactly as designed. Otherwise you risk pulling the wires causing them to break. Look at another car to see the correct route. Easy enough to check the continuity of the sensor.

For your rear lamps, check that the installed lamps are the ones shown in the manual. So many times people replace them with what ever fits. Don't use "long life" or "equal to" lamps. If 21W is specified, get it in the socket. Benz measures the current flowing to the lamp, if it is too high or low, it generally turns the lamp off and displays a problem on the MFD.

Good luck, and welcome aboard.

Moviela

If you are in the USA you can get a free subscription to the MBUSA electronic parts catalog. (EPC) It will allow you to put your VIN into the system and it will show correct part numbers for your car. Besides cookies at the Detroit auto show the EPC is the only thing you will get free from MBUSA.

pg043

Thanks for the detailed responses! I'm not sure what type of battery is in the vehicle, I will have to check when I get back home. I did have it checked at Autozone the day I picked it up and they said the battery was fine, whatever that is worth. Should I buy one and see if they'll let me plug it in in the parking lot before I keep it?

I did already replace the batteries in the key fob and it gave me no improved performance. I will check the coils in the rear windshield...I live in a warm climate so haven't needed to turn the rear defroster on yet.

About the brake sensor--The wire is definitely not broken. I can check the continuity of the sensor, but I'm guessing the problem is somewhere else down the line. Do you know where the brake sensor wire terminates so I can check the connection on the other end?

Alswag

You could check the battery voltage VIA the dash, that's where I'd start.
Turn the car to position 2 (Before fuel pump), and click the reset knob - the left of the tach - three times. It will bring you to a "secret" menu, and from there you can check your engine model, turn DYNO mode on, and check your battery voltage.
I'm not completely sure if it's the exact same process for the facelifted models, but pre-facelift it works.

pcy

About the brake pad sensor - there should be one on the front and one on the rear. It's possible the rear sensor was simply disconnected and removed. Not having the sensor will trigger that light, until a new/unbroken sensor is installed.

Moviela

The WIS indicates 1 to 4 sensors can be fitted to W/S203 chassis cars. It depends on the VIN and where in the world the car was sold. Many North American cars have a single sensor on the right front wheel.

pg043

What voltage should I be checking for? I'm not sure what is meant by a "flat" battery. Could this be the case even though Auto Zone hooked it up to their tester and found nothing wrong?

Moviela

A flat battery is like a flat tire. It is not filled with enough energy to keep everything working. The voltage should read 12.6 volts with the car stopped, everything off. During cranking (at ambient 68F and above) it should drop to 11.0 volts. After starting, a reading of 14.4 volts will be seen if the alternator is in fine fettle. After refilling the battery for a few miles, the voltage will drop into the low 13 volt range as the alternator current is reduced by the regulator. You don't indicate the mileage, but the alternator could be suffering from a worn poly-V tensioner, a bad bearing in the alternator pulley, or a misbehaving regulator.

The battery needs enough storage capacity to keep the voltage AND current available to all the consumers in the car. The battery is huge, and fills the entire space under the cabin filter. The battery should be rated 100 Ah for a flooded battery or 95 Ah for an AGM silver calcium battery. The later is a newer technology, but the silver about doubles the price of the battery.

Many people put a plain size 49 battery in the car. It fits, it will start the car, but the electronics are starved for current. A 70 or 80 Ah battery is like using a garden hose when a fire hose is needed. It will cause a lot of intermittent errors.

If it is an 80 Ah battery, the Autozone tester could very well say the battery is fine. The tester does not know the battery is too small.