Water in the ECU / Sam Unit!

northcave

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Ok so I posted recently about an issue of a 2001 C220 not starting.

The car was collected and my local merc specialists took a look. Seemed as though there was half an inch of water sat in the ECU and below Sam Unit. All the connections in the ECU had corroded.

However, they took it apart and stuck it in their airing cupboard overnight and now it works! So I got lucky this time.

But my question now is how on earth could water have got in there. I presume it cant get in from below and even with a downpour water wouldn't get under bonnet and run over the Sam unit in its location at the back of the engine bay.

Has anyone seen something like this before?
 
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northcave

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Update:

I thought I would run a hose onto the windscreen and see where the water went... most of it went where it should but i notices that some got through the rubbers that go around the wipers, allow water to drip through onto the top of the fuse box.

Does anyone know what the name / part number is for these little rubbers on a C200?
 

television

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Is it worth drilling a tiny hole in the bottom of the box, not good is it that water can get in
 
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northcave

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Is it worth drilling a tiny hole in the bottom of the box, not good is it that water can get in

Yes that's a good idea. I'll have to find a moment to figure out how the SAM unit comes out and what the CPU looks like underneath.
 

television

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If you can see the bottom a hot soldering iron will do it, a 1/4" tip will make a neat round hole
 

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