El aire acondicionado estaba haciendo un ruido raro, así que lo apagué.

Estaba haciendo is the imperfect progressive (imperfect of estar + gerund). It frames the noise as an ongoing background situation at that time: the A/C was making a weird noise (in progress), and then another action happened.

• Estaba haciendo = ongoing in the past (background)
• Hizo = a completed event: “it made (a noise)” as a single finished action (less natural here)

Yes, hacía un ruido raro is very common and often more natural. Both mean it “was making” a strange noise, but:

• Hacía (imperfect) describes a habitual/continuous past situation without emphasizing “in progress.”
• Estaba haciendo emphasizes the action as “in progress right then.” In many everyday contexts, they’re interchangeable.

Because turning it off is a single completed action with a clear endpoint: “so I turned it off.”

• lo apagué (preterite) = I turned it off (finished action)
• lo apagaba (imperfect) would suggest “I was turning it off” (in progress) or “I used to turn it off” (habit), which doesn’t fit the cause → result idea as well.

Así que means so / therefore, introducing a result or conclusion. Structure: [cause], así que [result]. Here: Weird noise (cause), así que I turned it off (result). It’s very common in Latin America and Spain.

Lo is a direct object pronoun meaning it (masculine singular). It refers to el aire acondicionado. Spanish commonly uses object pronouns instead of repeating the noun:

• …así que lo apagué = …so I turned it off You could say así que apagué el aire acondicionado, but using lo is more natural once the object is established.

Because apagar takes a direct object (what you turned off), not an indirect object (to whom/for whom).

• Direct object pronouns: lo / la / los / las
• Indirect object pronouns: le / les So: lo apagué = I turned it (the A/C) off.

The main noun is aire, which is masculine (el aire). The adjective acondicionado agrees with aire, so it’s masculine singular: acondicionado. That’s why later you also get lo (masculine).

Un means a (an unspecified noise): “a weird noise.” You’d use el if the noise is specific/identified in context, like a particular known noise:

• un ruido raro = some strange noise (new information)
• el ruido raro = the strange noise (already identified/expected)

In Spanish, descriptive adjectives commonly go after the noun.

• un ruido raro = a strange/weird noise (neutral, most common) Putting it before can change nuance or sound more stylistic:
• un raro ruido can feel more literary or can emphasize “how unusual” the noise is.

Raro is very common and natural for “weird/strange.” Alternatives you’ll also hear:

• extraño = strange (very common)
• inusual = unusual (more formal)
• como raro / medio raro = kind of weird (very colloquial)

Estaba (imperfect) sets the scene: the A/C was in a state of making noise (ongoing). Estuvo (preterite) would frame it as a bounded, completed time period: “it was (for a while) making a noise,” which is possible but less typical here unless you’re emphasizing that the weird noise happened for a specific, finished interval.

No. Spanish usually omits subject pronouns because the verb ending already shows the person:

• apagué clearly = I turned off You might add yo only for emphasis/contrast:
• …así que yo lo apagué (no él) = …so I turned it off (not him).