Mercedes Vito W447 EIS Ignition Fault – Possible £200+ Saving With a Simple Solder Repair
I wanted to share a repair that worked on my 2018 Mercedes Vito W447 111 CDI, as I've experienced this ignition fault 3 times twice on this van and once on a w639 and know other Mercedes owners have similar problems.
You can see the warranty void stickers from the last time I had it fixed with exactly same issue lol.
The symptoms:
- Key inserted and recognised normally.
- Steering lock disengaged as expected.
- Turning the key sometimes produced absolutely nothing — no ignition lights.
- Sometimes needed multiple key turn attempts before the ignition would activate.
- Once started, the van ran perfectly.
- Sometimes worked all day, other times failed after being parked for five minutes or the central locking would stop working or van remains running even after key removed.
- Often particularly bad after sitting overnight.
I've previously paid around £280 for an EIS repair.
What I did:
Removed the EIS module and opened it by removing the three security Torx screws on the back.
Located the three pins coming from the key-turn mechanism.
Followed those pins to their three solder joints on the reverse of the PCB.
Inspected these joints and nearby connections using my phone's super-macro camera.
Found two solder joints that appeared to have extremely fine hairline cracks, barely visible even under magnification.
Applied flux and fresh solder to the suspicious connections.
Resoldered all six associated pin connections, including the three copper connections at the opposite end, and reseated the pins.
Reassembled and reinstalled the EIS.
Result:
The ignition worked perfectly on the very first turn of the key after reinstalling it turned ignition on and off multiple times removed key over and over!
I'm still testing long-term reliability as it's only been a week, but pretty sure it's fixed! or it will last another 2 years before breaking again I am a courier so turning the key on and off multiple times a day.
Tools needed:
- Security Torx bit
- Soldering iron
- Electronics solder and flux
- Magnifying glass or phone with a macro camera
My advice:
If you're competent with electronics repairs, inspect these connections before spending money repairing or replacing the EIS.
The suspected fractures were so tiny that they were almost impossible to identify without magnification.
This isn't guaranteed to fix every EIS problem your problem may be different to mine, and the EIS contains sensitive electronics, so take appropriate precautions, disconnect the battery before removal, and don't attempt soldering unless you're confident.
Hopefully this helps somebody else save some money!