Since I'm new here, I'm going to throw this out there and never explain again about that "new part same problem issue" and my favorite of all is,
"My check engine light came on", which has never come out of my mouth.

My latest success story is a friend took my advice about his motorcycle that had sat inoperable for several years. Every electrical problem imaginable, a laundry list, unsalvageable pile of iron. I caught him before he ordered a list of parts. Bike cranks right up purrs now and not one light anywhere malfunctions and not one new part was purchased.

Words that have never come out of my mouth, "My check engine light came on..." Driving in swamping, puddled, torrential rain, wetter than wet soaked motor, multiple blizzards in mad weather, scare you to death weather if your car stalls and they do stall in blizzards. Main reason people are scared to drive in blizzards is cars will stall out and no one else is around. Smooth idle all day on my vehicles in all of these conditions. No codes thrown to date on one owner SUV; age 16 with 135,000 miles. Original starter, alternator, fuses, relays, sensors and all other original wiring components. My point being, it was the maintenance I did and not luck.

Electrical System Maintenance Procedure

Step (1) Avoid excessive rain/inclement weather driving and avoid heavy handed spraying with water hose jet nozzles every time the car is washed. My preference is low flow rinsing to clean with liquid waxes only, soap only if very dirty and greasy. If the following steps have been performed, this water encroachment can be mitigated. Say it with me folks, "Nothing electronic works well when wet. Wet circuitry is bad each and every day."

Step (2) Use proper safety equipment. Eye protection. Disposable latex gloves if you care about your hands. Cloth rags that do not create lint are helpful.

Step (3) Disconnect the negative battery terminal

Step (4) Identify each and every harness connection you are comfortable reaching and research how each coupling you see was designed to be released so you will not cause any damage

Step (5) Get your can of Electrical Contact Cleaner. Typically, only older weathered circuits need a very light spray, use spray cleaner sparingly and protect over spray with a small rag. Almost new connections can have oxidation as well and be unable to maintain 100% contact. Electrical connectors can and do drop below 100% for many reasons. The main 2 reasons are either loose/bent contact surfaces or dirt and corrosion/oxidation. If any electrical engineers want to go into specifics on sine wave interruptions at the hertz level for both smooth wave and pulse width modulated wave spikes, then more validation on the importance of dry and well connected circuitry is welcome.

Step (6) Get your tube of Dielectric Tune-Up Grease. Use sparingly on any plug/contact on the vehicle and never use dielectric grease on your battery, Negative (-) ground contacts or Positive (+) lead at the car power block. If you are not sure what I mean, just keep the grease off of anything with large gauge wire, battery side 12V high amp circuits create too much high potential sparking. That does not mean you cannot use it there, you can put it on those battery post connector sparingly. If you grease them excessively on the battery post, put a warning label on your battery "Do not connect this end last when jumping - Fire Hazzard, coating is flammable."

Step (7) Wrap it up and reconnect the negative battery terminal

That is all there is to it. Doing this will make you a believer. I've have never blown a fuse and that is not luck, no water has ever shorted in my system because I greased every contact about 15 years ago. Remember also, the more age a weathered car has, the more corroded connections in places you don't know exist. It is not practical to do every connector except when built, During any service on old or new cars that exposed hidden connections, ignoring this service quick step is almost sacrilegious in my book.

This procedure should also supersede any diagnostic code interpretations or part replacement in circuit subsystems. Remember, a code is nothing more than a pointer to wires in a vehicle. I will admit some parts can and do fail just not as you are led to believe. That brand new thingamajig that your swore fixed your problem when you "plugged it in" actually made the problem go away as a result of disturbing weak contacts during removal and reinstall, albeit temporarily in many cases.

If I helped just one person, it was worth writing this up.
Ernest Jones

 

I want feed back. You "hands on guys" at the end of your rope about why this or that circuit is not working and refuses to work. Clean and grease it.
If you think a Mercedes is difficult to tune, try playing with a dual point ignition from the sixties muscle car. Childs play in comparison.