Spare key wont lock or unlock the car

[Eduardglc]

Hi

My spare key won't lock or unlock the car. I can start the engine with the same key but just can't lock it or unlock it. I have always used the main key and the spare key has been in the key wallet signal blocker which has hardly been used.

Any tips would much appreciate it.

Thanks
Ed

 

[EmilysDad]

A change of key battery would be my first thought.

 

[Eduardglc]

Thank you. Do you know if the batteries recharge when you use the key everyday?

 

[SmartAmg]

Welcome, Eduard.

 

[drmw]

Thank you. Do you know if the batteries recharge when you use the key everyday?

It doesn't

 

[LostKiwi]

As above they are disposable lithium cells (CR2025 from memory but could be wrong).

 

[Naraic]

The only stupid question is the one not asked.

 

[Naraic]

A non rechargeable battery is used for locking and unlocking the doors. A battery in the key is not required to start the car.

 

[Blobcat]

As above they are disposable lithium cells (CR2025 from memory but could be wrong).

They are CR2025's

As an aside the "25" bit identifies it as 2.5mm thick - whereas a CR2032 would be 3.2mm thick

 

[LostKiwi]

They are CR2025's

As an aside the "25" bit identifies it as 2.5mm thick - whereas a CR2032 would be 3.2mm thick

That's it. 20=20mm diameter, 25=2.5mm thick.

 

[Eduardglc]

Thanks everyone! Appreciate your prompt responses. The battery was dead so I changed it and the key worked fine. You are correct about starting the car even when the battery is dead. Mercedes me app very useful in these situations.