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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53981
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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Never had this before but this is whats happening engage key

Customer Question

Hi Never had this before but this is whats happening engage key turn ignition on usually there is a noise of some kind dont know if it is the alarm system switching of or something else but the car will start emidiatley now when turning the key it brings on all electrics and the main fan but car wont start
JA: Is the car in "Park" or "Neutral?" Do you know if your car has a "wheel lock" feature?
Customer: Park I can only remove key when in park dont know about wheel lock future maybe describe please
JA: What is the model/year of your Mercedes?
Customer: S reg slk230
JA: What year is your Slk230?
Customer: 1977
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Checked for loose wires, trying to figure out why the fan is coming on this does not usually happen it is as if something is not switching on, Trying to think of ideas will this have a park start sensor
JA: Anything else you think the mechanic should know?
Customer: Yes would try to fix it myself, or get garage to fix depending on complexity of problem
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Mercedes Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi, my name is Marty.

Expert:  Marty replied 1 year ago.

This problem is caused by a bad K40 relay. The relay is located under the hood inside the module box.

Expert:  Marty replied 1 year ago.

Often times you can open the module box and tap on the relay while a helper turns the key to start the car. If you have no success you will need to replace the relay. The part number of the relay is 210 540 00 72. Click on the attachment for a picture of the relay.

Expert:  Marty replied 1 year ago.

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