Mercedes ML 430 will not start. No click, no electrical lights nothing.

Question

After taking a nap in the parking lot at my job, the driver's seat (power seating) -- the passenger seat did work-- I had laid back could not be readjusted. After work I went home (3am closing shift). Two days later no power whatsoever. I jumped the battery still no lights (electrical lights and headlights). Even when i turn the key over there is no sound or click. When I needed a new battery few months back, there was a distinct clicking sound. The battery is definitely good (new).

No previous electrical or wiring problems

But I still can't get the engine to turn over or the lights (oil, engine, ABS, etc) to come on when the key is turned to the second and third position.

                       Any ideas it is a Mercedes ML430 - 1999.

Answer 1

Check your battery across its posts, do not use any wiring or its clamp. Post to post with a voltmeter will tell you if you have power in the battery. Then with the red lead connected to the positive post, check for voltage on the vehicles negative cable clamp at the battery. Red lead connected still, check for voltage at the negative cable earthing end, and also check for voltage at the vehicle where the cable is bolted to the vehicle. You are looking for a large drop in voltage. Rectify any faults. If the battery and its connections are all OK, then the next step is the ignition switch. Check for a good feed and that the terminals are giving out a good voltage to the differant cables as you turn the key to its differant positions. Next along the line is the Multifunction Control Module in the engine bay, but you will now need a good auto electrician. Your Merc does have a DLC plug, but it is unlikely to be working with a complete power loss like you describe.

Answer 2

In addition to the other suggestions about battery voltage and ignition switch, check that the exciter cable (typically the "thin" one) that goes to the starter motor has no breaks in it and is firmly connected.

Check for obvious things like there are no blown fuses in the fuse box.

One other suggestion is to check that you've not trapped any wiring under the seat when it was reclined and you've not accidentally left an interior light switched on which could have drained the battery.

If it's a manual car, try bump starting / tow starting it and if it fires up that way, it points to a problem with the starter motor or wiring around that.