Mercedes Fuse Box / SAM Replacement, Windshield Wipers

Andrew Technician Commack, New York Posted   Latest  
Tech Tip
Electrical
2003 Mercedes-Benz C230 Kompressor 1.8L 5-spd (722.6)
Wipers Inop
Front Sam
Rear Sam

A shop had a car that wouldn't crank when the key was turned but started if the starter circuit was jumped. The front SAM was faulty, but when it was replaced the engine still wouldn't crank with the key and it no longer started when jumped. Additionally the wipers quit working 

The issue was simple - the new SAM came with some fuses missing, the fuses for the ME. The wipers didn't stop working, they just don't work whenever the hood or driver's door is open on most MBs since the 203 chassis, something that is not well known by shops that don't work on a lot of Mercedes.

Always compare the new and old SAMs, sometimes fuses and even relays are missing. Also, for authoritative information on fuse location, assignment, amperage, circuit, and consumers, see group 54, subgroup 15 in WIS. (Attached).

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Michael Owner/Technician
Cartersville, Georgia
Michael
 

I've learned that the hard way myself! Working on air suspension with the door open!! I have one a W203 in here now with a no spin no start. ME and front Sam sitting in water that came from the carwash. He's calling the carwash to see if they'll pay for it since it happened there!!

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Maurice Business Development Manager
Geebung, Australia
Maurice
 

Great Tip Andrew about fuses not being fitted to the SAM that would definitely catch some Techs out. A lot of Euro cars will not allow the wipers to work when a bonnet is up. Not long ago my tech tried to bled the fuel after replacing a fuel filter and could not turn the lift pump on in a VAG Diesel Golf. The scan tool reported select P/N we are thinking what is P/N it took a while to realise

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Bob Diagnostician
East Longmeadow, Massachusetts
Bob
 

On vehicles like this will the engine crank if you close the latch with the hood open or are there other switches involved?

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Michael Owner/Technician
Cartersville, Georgia
Michael
 

I think Andrew was making a general statement about front SAM replacement. When you replace it you make sure all of the functions work before you release it to the customer. If you're chasing a wiper problem then trip the front latch before testing or you're always going to have to no trigger to the motor as your diagnosis!!

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Bob Diagnostician
East Longmeadow, Massachusetts
Bob
 

I was just asking a general question on the hood operation. It is as simple as closing the latch to defeat to no start strategy or are there other measures that need to be taken if you want to crank the engine with the hood open?

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Maurice Business Development Manager
Geebung, Australia
Maurice
 

Hi Bob, the engine will start and run with the hood up it is just the wipers that will not operate until the hood is closed, possibly so the wipers will not get caught up on the open hood. Guys just a bit of trivia, down under here in Australia we call the car roof or turret the hood, and what you call a hood we call it a bonnet. What you call a fender we call it a mudguard, what you call a

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