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Matt, Engineer
Category: Mercedes
Satisfied Customers: 21256
Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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I have replaced the battery in the key but It won't turn the

Customer Question

I have replaced the battery in the key but It won't turn the ignition on. nothing works yet it has been driving great fro an old car. What is the problem?
Submitted: 9 months ago.
Category: Mercedes
Expert:  Matt replied 9 months ago.


1st thing to check that if the main battery in the car is up to charge and holding at least 12V during cranking

if its not then try charging it up or possibly consider replacement if its over 5 years old

if this is OK then try a vehicle reset, where you remove the battery cables and secure them together for 10 mins to discharge all the capacitors around the car

and then when you reconnect the battery , ensure that the keys are in your hand as the alarm may go off

Expert:  Matt replied 9 months ago.


do you still need help?

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Customer: replied 9 months ago.
I had already checked your answer & eventually called out the AA. It requires a new key to be programmed. So that was a waste of money. I'll never do that again.