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Hi i have random electric issues with my car where i have High beam indicator on dash with no headlight control
Emergency brake indicator on dash
Airbag indicator on dash
No blinkers
Heated seats not responding
Front right srs malfunction indicator
Cooling Fan wide open
Temp gauge not reading
and after i have the issue when i turn my car off it takes a little bit before it will start back . Key will come on and all lights come on but vehicle doesn’t even attempt to turn over
Originally i assumed it was the alternator so i had battery and alternator tested and they came back good . I came across the “infamous?” F32 prefuse box issues where i read of similar issues so i found a video showing the inside with all the fuses and relays . I tested continuity from the ground of battery to all of the post on the box and all had continuity circled in green . The one circled in red didn’t have continuity but also from what i can tell nothing is hooked to it . So i guess two questions , one , should the red circled post have continuity and mine doesn’t so that’s my issue or two can the fuses be good allowing continuity but have a bad relay that still causes the issue ? Also the car wasn’t showing any of the issues while testing for continuity. Should i have to check whole issues are showing? I hate to order a $400 replacement and that not be the issue . Thanks for any help
I say front sam because most if not all the faults you list seem to be running off it, headlights, ESP, parking brake indicator light, radiator fan etc. I have seen a few posts from people with similar issues and replacing the sam resolved it. I think most people had some sort of water issue, I remember someone took the lid off it and didnt put it back on or close it right, someone else said there sunroof drain was clogged and water got in it.
Have to use a Mercedes specific scanner and find all the fault codes.
The sam doesnt just hold the fuses and relays, its a big circuit board like a computer.
All of the comments are good ones especially the ones suggesting scanning for errors. Pre-fuse box failures are not common. And they are usually the result of tinkering under the hood and shorting something to ground.
There is only one relay in the W204 pre-fuse box, the quiescent current relay that disconnects power consumers to save the battery for starting. The rest are fuses. Mercedes doesn’t sell parts, but there’s nothing in that box that a DIYer can’t replace from online catalog parts. Do some searching and find some completely competent repairs in this forum.
Here is a thread I came across. It mentions that pre-fuse (post# 6) and the front SAM (post# 12). Though the issue seems to have started after a car wash.
02-08-2024, 11:10 AM
