If I give my machine to a repair service how do I secure my wallet?
Unauthorized access to your wallet and unauthorized Ada transfers
Never keep your password or your 12-word Daedalus wallet recovery phrase on your computer unencrypted (this applies to all users at all times, not just to this repair scenario).
An unauthorized person like a technical support technician cannot spend money in Daedalus without knowing your spending password. They cannot reset your password without knowing your 12-word Daedalus wallet recovery phrase.
If you do have your password or passphrase on your computer unencrypted then you should encrypt it or remove it (and ensure it is also removed from your trash) before allowing anyone to access your computer.
As a final note, once you get your computer back from the repair shop you should always check to make sure no unauthorized changes have been made to your system. After logging into the computer the first time after repair, you should perform a full scan of your computer using antivirus and malware detectors prior to performing any actions requiring you to enter sensitive information (e.g. online banking, initiating a transaction in your Daedalus Wallet, etc).