W204 Rear SAM Problem

[lange07]

My name is Lucas, I'm new here and I have a very defective car.

I had some electrical issues with my C200 compressor. To summarize, about a year ago I had to replace the front SAM module in my car (I had to import a new sealed module from Germany) and repair the rear SAM module. The car actually went into "limp mode" turning off all non-essential electrical parts while other things stayed on while the car was parked, draining the battery (4 in 1 year). After replacing and repairing everything worked fine for a few months, the front SAM module had no issues until the car again exhibited some of the same faults as before, but this time instead of turning everything off, it flashes the entire panel as if it is trying to work but stops and stays in that cycle. I sent it to the same technician and it turned out the rear SAM module was faulty. The repair was repeated by replacing one of the chips in the module and setting it up for the car to accept. 3 weeks later, same problem.

So, does anyone know what could have caused the module to burn out twice (well...three times since it was rebuilt along with the front SAM) with the same defect? Has anyone had a similar problem with one of these vehicles?

By the way... funny, I know that the car will start showing the problem, flashing everything and turning off half the buttons when the sunroof button stops working, as well as the gasoline indicator and high beam

 

[bigchevy66]

The only time I remember seeing multiple SAM failures was due to unauthorized water ingress. Have you looked at the old SAM to see if there is any corrosion inside or on the connectors?

 

[lange07]

My sunroof drain is clogged, water got into the passenger footwell but not into the modules, they are dry and have no obvious signs of water ingress (like corrosion or stains), but I will check again. Thanks

 

[bigchevy66]

Oh, then most likely you have corrosion inside the CAN blocks, or other connectors, in the passenger footwell. Visually inspect the CAN block, connectors, and the board inside the CAN block. Unfortunately, if the corrosion has been there a while it will "wick" up the wiring and it will be difficult to find a clean section to make a repair. You'll usually see the copper strands of the wire have turned black.

Clogged sunroof drains are a very common issue on W204s.

 

[B0bby92]

I had problems with the front SAM. I sprayed all the fuse boxes and connectors with Wruth contact cleaner. I waited a few minutes and started the car. There have been no problems since then. Everything was perfect for 3-4 months already. It displaces moisture and cleans contact surfaces, restores pistons and ensures good communication. I suggest you try this before replacing

 

[lange07]

Already looking for a new SAM, but I will definitely consider this solution, thanks.