S211 keyfob ignition issue

[repvik]

My spare key has started to act funny. I can lock/unlock the car just fine, but nothing happens when I insert it in the ignition. If I insert the key and then press either lock or unlock, the car "wakes up" in the same manner as when I insert the other, working key.
Any way to fix this, as the local stealership takes close to USD500 for a new key

Car is a 2004 220 CDI S211

 

[television]

Hello and welcome, the transponder coil will have fallen off, you can get a key from Ebay and transfer the coil to your key

 

[repvik]

The coil appears to be firmly attached to the PCB. Can try to resolder. If that's not the cause, what could it be?

 

[television]

The other fault on the keys is that the through plated hole on the PCB can go partially open circuit, I have a test rig for checking them. it means checking the voltages both sides of the PCB, to fix I insert a thin strand of wire and solder both sides.

That coil is 2.2mh and measures under 2 ohms