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W204 c220 alternator issues

Gfromleeds

Active Member
Joined
Mar 13, 2024
Messages
67
Location
Uk
Car
C220
Morning guys I've started a new thread as my other thread discussing this was originally about another issue!
So I'm having alternator/ power problems
Every now and then over the last few weeks, the battery warning light randomly comes on! Turn it off restart, and it stays off for a few days!
However a few days ago when starting in the morning, the battery only just started it! Withing about a mile, all kinds of nightmare messages started coming up on the dash.
I pulled over and shut it down only to find when restarting the battery was completely dead! "Click"
Got my mate to come jump start me and everything was fine untill we took the jump leads off, then all the warning messages came back! But since I was running i headed back home! Found nothing was working!
No windscreen wipers, no radio, even the gearbox was stuck in 1st gear!
Got home put my battery charger on it and it reported under 8%charged! Let it charge for a few hours and she started up just like normal. No warning lights (not even a battery/alternator warning)
So I'm suspecting the alternator is goosed. However I have a niggling feeling it's something else! Why would the battery light not be on if the alternator not charging?
A few weeks ago I had the auxiliary belt replaced as the old one jumped off on its own and since when I start it up or shut it down I hear a chirp come from the belt area! Could a slipping belt cause such charging issues? The belt feels quite tight and the power steering works fine unless pushing against full lock, where it gives short chirps!
Anyone any ideas?
Im not against a new alternator i just don't want to waste a few hundred quid and most of an afternoon fitting it if it's something else!
 
I've heard there's a dedicated fuse for the alternator! Anyone know where this is? and what type it is? I imagine it'll be a special fuse
 
Am i reading the dash correctly that its minus 38amps?
Because it jumps up to minus 90amps when i rev it!
20250318_170257.jpgScreenshot_20250315_163737_Torque.jpg
 
Try this to test battery and alternator.
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Those voltages are far too low. Do you know the condition of the battery?
68151.jpg
 
I've a digital battery charger that I've been using to charge overnight so I can still using the car to get to and from work! and each morning the charger is reading full charge and when I get home at the end of day it reads around 20% charged so that scale is about right! Ive now got a replacement alternator which I'll be fitting Saturday! Hopefully that will be an end to it as I've had nothing but hassle with this car over the last 2 months
 

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