Learn Hardcore Russian: Выключатель сломан, поэтому свет не выключается. - The light switch is broken, so the light doesn’t turn off.

Because выключатель is the grammatical subject of the first clause: Выключатель сломан = The switch is broken. In Russian, the subject is normally in the nominative.

What is сломан exactly—an adjective or a verb?

Сломан is a short-form passive participle (often taught as a “short adjective” because it behaves similarly). It agrees with the subject in gender and number:

выключатель (masc.) сломан
кнопка (fem.) сломана
окно (neut.) сломано
выключатели (pl.) сломаны

It describes the resulting state: broken.

Why is there a comma before поэтому?

Because there are two separate clauses: 1) Выключатель сломан
2) свет не выключается

Поэтому connects them as a result/consequence, and Russian normally uses a comma to separate clauses in this structure.

What does поэтому mean grammatically, and how is it different from потому что?

поэтому = therefore / so / that’s why (it introduces the result).
Structure: Cause, therefore result.
Выключатель сломан, поэтому свет не выключается.
потому что = because (it introduces the reason).
Structure: Result because cause.
Свет не выключается, потому что выключатель сломан.

Both are possible; they just package the information differently.

Why is it свет не выключается and not свет не выключает(ся) with a direct object?

Because выключаться is used here as an intransitive “turn off (by itself / cannot be turned off)” type verb. That makes свет the subject (nominative), not an object.

Compare:

Я не выключаю свет. = I’m not turning off the light. (transitive: выключать + object)
Свет не выключается. = The light won’t turn off / can’t be turned off. (intransitive: выключаться)

What does the -ся in выключается mean here?

Here -ся signals a meaning like “gets turned off / is able to be turned off” (often called anticausative/passive-ish usage). It focuses on what happens to the light, not on who does it.

So не выключается often implies it doesn’t switch off even when you try.

Why is выключается in the present tense? It’s about a problem right now.

Russian present tense of the imperfective is commonly used for:

what is happening now, and/or
what is generally true in the situation right now

So свет не выключается means it doesn’t turn off (when you try)—a current, ongoing inability.

Could I say не выключится instead of не выключается?

Yes, but the nuance changes:

не выключается (imperfective) = it doesn’t turn off / won’t turn off (in general / when you try repeatedly)
не выключится (perfective future) = it won’t turn off (this one time / as a single result)

In troubleshooting contexts, не выключается is very natural because it describes the persistent problem.

Is свет literally “light” or does it mean “the lamp” / “the lights”?

свет can mean:

“light” in general, and very commonly
“the light” as in the light in the room / the lights

So свет не выключается is a standard way to say the light(s) won’t turn off, even though it’s not naming the lamp explicitly.

How is word order working here—could the sentence be rearranged?

Yes. Russian word order is flexible; it changes emphasis more than basic meaning. For example:

Выключатель сломан, поэтому свет не выключается. (neutral)
Свет не выключается, потому что выключатель сломан. (result first, then reason)
Поэтому свет не выключается: выключатель сломан. (more “explaining” tone)

The key things that stay stable are the clause structure and the conjunctions (поэтому / потому что) plus the comma/colon punctuation.