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Discussion Starter · #1 ·
I recently started having problems with my car and I'm not sure where to start looking. Back several months ago, I had a low voltage code in my car. Put in a remanufactured Bosch alternator at the recommendation of the local Benz shop. Didn't fix it. Turned out to be the K40 relay, so in went a new one. That seemed to fix the issues I was having. Within the past week, I started having problems with the lights on my dash fading and flickering. Everything seemed to be OK as long as I wasn't running the heat, my headlights, radio, etc. I went by a German repair shop and they load tested my alternator. I'm not sure what measurement they were using, but they told me my alternator was only putting out 50 of whatever, when the normal amount should be 100. They recommended replacing the alternator. At this point, I did not replace it. I went by Advance Auto and they said my alternator was putting out 14 volts and it was fine. Well, then the problem got more prominent and I started having drivability issues at night when I was using my headlights. What would happen was the dash lights would fade, my headlights were flashing, and two lights (ABS and ESP? I was in freak out mode, so I can't swear which lights they were) would flash, and my check engine light would flash. They would all flash in harmony and with each flash, my engine would feel like it was breaking. Almost like I was hitting the breaks then letting off in approximately 1 second interval pulses. I was talking to a mechanic that does not really work on Mercedes and he said it sounded like it was low voltage to him. What could cause low voltage? Even though my check engine light was pulsing with all the other lights, it never stayed solidly lit and there were no codes stored. The engine pulsing has now gone away and the check engine light is not on, but I can still see my dash lights "sparkling" very faintly. Last night on my way home, we had on the radio and my window was cracked. My daughter reached over to roll up my window, and the lights flickered and the radio cut out for a split second.
 

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Check your main battery ground and make sure it is clean and secure. Even if the alternator was going bad, the battery should cushion any voltage changes. Look for the obvious, theses cars are getting old. Grounds are usually overlooked during troubleshooting.
 

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2005 SLK55 AMG /2005 SLK350
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I doubt it, but you never know with electrical issues. I would first to check the big negative cable between the battery Negative post and the car. Then I would check the big fuses next to the battery. It does sound like you have a fundamental issue. You'll need to use an ohmmeter, expecting 0.0 ohms, and wiggle the items while you're testing them.
 

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Discussion Starter · #6 ·
I doubt it, but you never know with electrical issues. I would first to check the big negative cable between the battery Negative post and the car. Then I would check the big fuses next to the battery. It does sound like you have a fundamental issue. You'll need to use an ohmmeter, expecting 0.0 ohms, and wiggle the items while you're testing them.

I don't know much about electrical drains in cars, but I did do a drain test a few weeks ago following the steps on a YouTube video. I had my meter hooked up to the battery and pulled each fuse watching for a drop. When I was working on the fuses inside the cabin (the little box on the driver's side to the left of the steering wheel), when I pulled the fuse for the high beams (cannot remember fuse number), there was a drop. I told the guys at the German shop about this prior to them testing my alternator, and they said that was normal. I didn't see how that was "normal" being that my car was completely off and the high beams shouldn't be drawing current...at least in my mind it shouldn't be LOL. After seeing the drop, I wasn't sure where to go from there so find out what was wrong. (just FYI, I had to open my door to get to the fuses inside, but I clamped down the door sensor and let it sit for about 30 minutes before performing the test).
 

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Could this rusty engine ground strap with a few broken wires be the cause of the electrical gremlin living in my car?
The ground itself should be sound, even if there are a few strands broken. The important thing is to have both ends brushed clean and where they connect to the chassis and engine, clean and corrosion free as well. There are other grounds on the left and right fender that also need to be inspected / cleaned if required.
 

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Discussion Starter · #8 ·
Woops. Looks like I accidentally deleted my last post when trying to edit. Long story short, the alternator, starter, battery are all in good working order. The battery post/cables and ground points have all be cleaned. No changes in dash light flickers.
 

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Discussion Starter · #9 ·
Yesterday I was pondering this whole wiring issue. I took a peek at the wires/connections from where I had removed my PSE when I first got the car. The reason I removed it was because it was soaked with water. Apparently it had been soaked for quite a while because the board was so corroded that there was no hope for saving it. I had to literally pry the connectors out because they had so much build up on them, they were pretty much fried into the PSE. I didn't realize at the time that I should have put electrical tape around the ends, and I had left the wires just dangling. It looks like the wires were hot because one wire had blue colored corrosion leaking out of it. What's the best way to remove any and all "juice" from these wires to ensure there's no voltage going to them? I don't really have the funds right now to buy the PSE. I did take the wires and put electrical tape around them so they wouldn't be touching any metal, but even then I still had a slightly drained battery this morning. As a side note, after I moved the wires around, I noticed that the button inside the car for "towing on/off" had a very slight illumination of the red light in the button's center which had not previously been lit. It didn't appear to be fully lit, just a slight glow.
 
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