Use of "no fault" (passive, accidental?) SE

Hola Daniel B.

Thanks for your thoughtful question! This is a common area of confusion, so you're definitely not alone!

To start, the terms "no-fault se", "accidental se", and "passive se" do not all refer to the same thing, although they can look similar on the surface. The accidental or no-fault se is used when something happens unintentionally, it's a way of expressing that the action was out of someone’s control. This structure uses se plus an indirect object pronoun (like me, te, le, etc.), and the verb agrees with the thing that was affected. For example, Se me rompió el ordenador means “The computer broke on me”. This implies it wasn’t your fault, it just happened.

In contrast, the passive se is used when the subject (the doer) is unknown or unimportant. For instance, Se vendieron muchos libros means “Many books were sold”. There’s no mention of who sold them — the emphasis is on the action itself. Finally, there's also the impersonal se, which refers to actions done in general or by people in general, such as Se vive bien aquí (“People live well here”).

Now regarding your sentence: “Yesterday I fixed his computer, and he has already broken it”. A good Spanish version of this would be: Ayer le arreglé la computadora (or el ordenador) y ya se le ha roto. Your instinct was very close! In the second part, se le ha roto is the correct accidental se structure. You’re right to include le to indicate “to him”. You don’t need lo here, though — the verb romperse is being used intransitively (it broke, not “he broke it”), so the direct object pronoun lo isn’t appropriate.

So, the final sentence — Ayer le arreglé la computadora y ya se le ha roto — nicely captures the meaning: that you fixed it for him, and it’s already broken again, presumably without him meaning to break it.

Let me know if you’d like more examples of how this works with different people (like se me, se nos, etc.). Happy to help!

Saludos

Silvia