barrysanders204

I own a 2006 Mercedes-Benz S500 4Matic, I've had some issues recently.

First off, my passenger floor got wet and I began having issues where the key would not turn in the ignition, so I could not start the car suddenly.

My current issue is that my trunk is not opening. The battery is disconnected, I only have one key, the mechanic metal key that I had used in the past to open the trunk, is not turning the lock at all. I can get the key in but it wont turn. My trunk is shut, with the battery charger inside and the battery disconnected.

What is the most efficient way for me to access my trunk?

Or does anyone have a solution or idea as to why my mechanic key is no longer turning in the lock?

I tried to remove my rear license plate to see if there were bolts or anything I could remove to get the trim housing off, but there just seems to be a small metal almost nail-like structure holding the trim on.


I am more worried about the trunk currently as I may have found a solution for my ignition, not sure on that, but having the battery connected again will obviously allow me to continue troubleshooting that, but until I can access the trunk, I am stuck.

I have been fighting this issue for weeks now, and have done quite a bit of research so I would really appreciate some quick assistance.

Thank you for your time.

wallyp

Pull the carpet back in the right front floor, remove the aluminum panel. Hook a good 12-volt battery, or a very good battery charger, positive connection to the heavy red wire, being very, very careful to avoid erroneous connections or short circuits. Hook the battery or charger negative connection to a good body ground point. Your key should now open the trunk.

With the trunk open, lubricate the key slot and work the key several times.

Carefully check the exposed pre-fuses for corrosion or blown fuses. Clean the connections if there is any doubt of their quality. Again, be very, very careful to avoid erroneous connections or short circuits! You must clean the drain hole in the bottom of the HVAC plenum under the right side of the hood, near the firewall, and you must keep it clear, as that is where the water entered the car. You must thoroughly dry the carpet and padding/insulation. You must remove the rear seat bottom cushion (release latch at each forward bottom corner) and carefully check the SAM (Signal Acquisition Module) under the right side of the seat. Water in this fuse/relay/computer box will cause corrosion, which will cause you endless problems.

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barrysanders204

Thank you for your quick response! Would it make any difference if I currently have the negative disconnected on the battery in the trunk?

Also, I tried to jump it but we did not have any luck.

wallyp

You must hook the outside battery to a point that feeds the car systems. It doesn't matter whether the ground cable is connected or not. Don't try to jump-start from these connections - doing so will possibly blow a main fuse or cause other damage. All you want to do at this point is to get the trunk open. If you have already blown a main fuse, you will need to connect to a point on the load or downstream side of the fuse, not the battery or power side of the fuse. If you are using a battery charger for the power, remember that most modern chargers will not provide power to a dead circuit - they are designed that way, as they are designed to charge a battery, not act as a power supply. There must be a mostly-charged battery on a circuit before the charger will provide power.

barrysanders204

Thank you Wallyp! I was able to get into the trunk. Now I'm off to troubleshooting the ignition again.

The cars passenger footwell got wet, since then I have had some issues. When I put the key into the ignition, the key will not turn at all. I only have the 1 key. I have had a few issues in the past with getting the key to turn, but not much. Now I cannot get it to turn at all.

I have attached a few pics here that my Dad helped me with since he is far better at mechanical issues than me. Our question is, are those wires (the pink and red ones) are those supposed to be "hot" all the time? We put a test light on that wire and we did not get it to show that it is hot. Also, the other smaller cluster, I believe it is 3 smaller red wires, are those always hot too?

From looking up fuses, I also noticed there is a small fuse box down by the big red positive cable on the floorboard. My question here is how do I check/troubleshoot those fuses? My feeling is that my issue likely falls in that area since that was where the water was.

Thank you for any help. I may have to create a new thread to generate more responses here. I will do so in a day if this doesnt work.

wallyp

Your first goal needs to be to learn how to check the fuses. These are major power circuits, and yes, they are all hot all of the time (identified as "30" circuits on wiring diagrams). A voltmeter or multimeter will tell you if there is voltage present, but will not tell you if the power level is adequate. Think of the major positive battery cable, that must furnish power to operate starter and all electrical circuits in order to start the engine. Now, imagine that the cable has flexed for years, and is broken inside the insulation - except for one little strand of copper. If you test the cable with a voltmeter, you will find full battery voltage - but it will never start the car, because it cannot carry enough power.

The connections on the major cables that you are checking might be good enough to show somewhere close to 12 vdc, but there might well be enough corrosion from the water to prevent the connections from passing enough current to correctly operate the car.

Despite that possibility, the first thing that you must do is to determine if the fuses are faulty. The test light will show you that. Clip one test light connection to a good body ground - and it is vital that this be a good connection. You must then get access to both sides of each fuse, and determine if there is battery voltage on both sides.

WARNING: One side of each fuse is connected directly to the battery positive by a heavy cable. If you allow that live connection to touch the body, you can create a major short-circuit that can do MAJOR damage, up to and including setting the car on fire! Use extreme caution!

To reiterate in different words - every connection in this under-floor area must have full battery voltage at all times. The best way to start is to remove the negative battery cable connection, and make certain that it cannot creep back to the terminal and make a connection. The springiness of the cable can very well allow it to do that, so make sure that the cable end is held away from the battery post.

With the negative cable disconnected, you can freely disassemble each of the under-floor connections, clean all connecting surfaces, and check all of the fuses with an Ohmmeter. Do only one connection at a time to ensure that it goes back together exactly as it came apart. Take numerous photos before and during the process!

Once all connection and fuses have been checked, reconnect the negative battery cable. You need to do that quickly and firmly - you do not want to be delicate here - you want the connection to be like turning on a switch, not dancing the connection so that you get spark after spark and voltage surge after voltage surge.You will get a healthy spark upon first connection. You do not, however, want to tighten the clamp bolt at this point - you want the terminal firmly seated on the post, but not tightened. Immediately check all of the cables and connections that you have worked on for any heat. If any cable or connection is noticeably warmer than ambient temp, immediately disconnect the negative terminal and start rechecking your work.

If you do not thoroughly dry the padding and insulation, you will get continuing corrosion that will continue to cause major problems.

I strongly suggest that you also remove the rear seat cushion and check for moisture in and around the SAM. Corrosion here will cause continuous problems.

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