Ya sea de día o de noche, mi madre siempre enciende los faros antes de salir a la carretera.

Ya sea ... o ... is a set expression meaning whether ... or ....

So:

• Ya sea de día o de noche = Whether it is day or night / Whether by day or by night

It is commonly used to present two alternatives, often in a slightly formal or polished way.

Other examples:

• Ya sea en casa o en el trabajo = Whether at home or at work
• Ya sea solo o acompañado = Whether alone or with company

A more everyday alternative in some contexts could be:

• Sea de día o de noche
• De día o de noche

But ya sea ... o ... is perfectly natural.

Sea is the subjunctive form of ser.

Here, ya sea ... o ... uses the subjunctive because it introduces alternatives in a fixed expression. It is not really stating a concrete fact like it is day; instead, it means whether it be day or night.

So:

• es = indicative, plain statement: it is
• sea = subjunctive, used here in the expression ya sea ... o ...

You do not usually replace it with es in this structure.

Literally:

• de día = by day / in the daytime
• de noche = by night / at night

These are very common Spanish time expressions.

Examples:

• Trabajo de día. = I work during the day.
• Conducir de noche me cansa. = Driving at night tires me out.

English learners sometimes expect por el día or por la noche everywhere, but Spanish often prefers these shorter expressions:

• de día
• de noche

Both are very natural here.

No, that would sound unnecessary and unnatural here.

In ya sea de día o de noche, the subject is not explicitly stated because Spanish often omits subjects when they are understood from context or when the structure is impersonal.

This expression works almost like a fixed phrase. You can think of it as:

• whether it be day or night

Spanish does not need to repeat an explicit subject such as ello or a full clause.

Yes. Although faro can also mean lighthouse, in the context of a car it means headlight.

So:

• un faro = a headlight
• los faros = the headlights

In a driving sentence, encender los faros is completely natural.

You may also hear:

• las luces = the lights

For example:

• Enciende los faros = Turn on the headlights
• Enciende las luces = Turn on the lights

Faros is a bit more specific than luces.

In Spain, encender is the standard verb for turn on / light.

So:

• encender las luces
• encender el motor
• encender la televisión

In some parts of Latin America, prender is also commonly used for turn on, but in Spain encender is the safer and more standard choice for learners.

So this sentence sounds very natural for Spain:

• mi madre siempre enciende los faros

Because adverbs like siempre often go before the conjugated verb in Spanish.

So:

• mi madre siempre enciende los faros

is the most neutral word order.

Other placements are sometimes possible for emphasis, but this is the standard one.

Compare:

• Siempre enciende los faros. = She always turns on the headlights.
• Mi madre siempre enciende los faros. = My mother always turns on the headlights.

Because after antes de, Spanish often uses an infinitive when the subject is the same as the subject of the main verb.

Here, the person who turns on the headlights and the person who goes onto the road is the same person: mi madre.

So Spanish uses:

• antes de salir = before going out / before setting off

If the subject were different, Spanish would usually use antes de que + subjunctive:

• Mi madre enciende los faros antes de que anochezca.
  My mother turns on the headlights before it gets dark.

Or:

• Mi madre enciende los faros antes de que salgamos.
  My mother turns on the headlights before we leave.

It means something like:

• to head out onto the road
• to set off onto the road
• to pull out onto the road

Salir by itself means to leave / to go out.
Adding a la carretera gives the idea of entering the roadway or beginning the drive.

So this is not just leave the house in general; it specifically connects the action to driving.

Because Spanish normally uses the article here: la carretera.

So:

• salir a la carretera

Literally: to go out onto the road

Spanish uses articles more often than English does. English often says just onto the road, but Spanish usually says a la carretera.

Yes, depending on the situation.

• carretera = road, usually a road for driving between places
• calle = street
• autopista = motorway
• autovía = dual carriageway / major highway in Spain

So if the context changed, you might say:

• antes de salir a la calle = before pulling out onto the street
• antes de incorporarse a la autopista = before joining the motorway

In this sentence, carretera is a general and natural choice.

Because enciende only tells you it is he/she/you (formal), not exactly who.

Spanish often drops subject pronouns like ella, but noun subjects such as mi madre are still used when you need to identify the person.

So:

• Mi madre siempre enciende los faros = My mother always turns on the headlights

If you removed mi madre, the sentence would become:

• Ya sea de día o de noche, siempre enciende los faros...

That would mean she/he always turns on the headlights..., but the listener would need to know from context who that person is.

Both are possible, but they feel slightly different.

• mi madre = more neutral
• mi mamá = more affectionate/familiar; very common in many regions
• mamá = very personal, like saying mum

For a neutral example sentence, mi madre is a very good choice. In everyday family speech, many people might say mi madre or mi mamá, depending on region and personal style.

Yes.

• enciende los faros = turns on the headlights
• enciende las luces = turns on the lights

The difference is that los faros is more specific. Las luces can be understood as the car lights in general.

If the goal is to emphasize safe driving before setting out, both work, but los faros points more directly to the headlights.

Yes, it is natural and grammatical in Spain.

A speaker from Spain might also say similar versions such as:

• Sea de día o de noche, mi madre siempre enciende los faros antes de salir a la carretera.
• De día o de noche, mi madre siempre enciende los faros antes de salir.

But the original sentence sounds correct and idiomatic.