PeachParts Mercedes-Benz Forum - View Single Post - Engine keeps running with ignition key out

CharlesJones · #3 11-06-2010, 05:39 PM

Thanks for the reply Yak - that's very helpful, and I have tried a few extra tests like you suggest. My car doesn't appear to have a "key left in ignition" warning buzzer - well not one which works anyway - but it does have a "left the lights on" warning buzzer which sounds if I open the drivers door with the keys out of the ignition whilst the lights are on. That warning buzzer still works even though the engine is still running when the keys are out of the ignition.

I also tried pressing the sensor/switch near the door hinge which is triggered by the door closing. There are two such switches on the drivers side, and just one on the passenger side. The upper most switch on the drivers door causes the "lights left on" buzzer to sound and also the courtesy light to come on and go out when entering/exiting the car. If I operate this switch manually with engine running/keys out of ignition whilst the lights are on, the warning buzzer will stop as expected. Also, I can switch off the courtesy light by holding the switch in, so it looks like this upper switch is working.

As regards the lower sensor/switch, if I operate this switch manually whilst the engine is still on/keys removed from the ignition, then the engine immediately shuts down. That was a great suggestion to try this to eliminate vibration as the cause of engine shut down, and I can confirm that it is definately this lower sensor/switch which is shutting the engine down. I haven't a clue what function this sensor/switch normally performs. The switch is only present for the drivers door, and doesn't control the courtesy light nor the "lights on" warning.

Do you have any ideas what that lower door-close sensor is normally for? Any other suggestions of any diagnostics I might try?

Many thanks for your help. I think I will probably be spending tonight trawling the Internet for any clues about what the fault might be. I thought it might be a faulty ignition switch - I can see how that might cause the engine to not shut down, but I can't see how it would make that lower door sensor shut the engine down! Electrics are so weird sometimes!