La mecánica revisa la batería porque el coche no quiere arrancar.

Because the subject is a female mechanic. In Spanish, many job nouns change form by gender:

• el mecánico = the male mechanic
• la mecánica = the female mechanic

One important note: la mecánica can also mean mechanics as a subject or field, but in this sentence the context and the verb revisa make it clear that it means the female mechanic.

Revisa is the third person singular, present indicative form of revisar.

So:

• revisar = to check / to inspect / to examine
• revisa = she checks / he checks / it checks

Because the subject is la mecánica, here it means the mechanic checks or the mechanic is checking, depending on context. Spanish present tense can often correspond to either English simple present or present progressive.

Spanish usually uses an article with countable nouns much more often than English does. So la batería is the normal way to say the battery.

Here, the battery is understood from the context: it is the battery of the car. Spanish often uses the definite article instead of a possessive when the relationship is obvious.

So this sounds natural:

• La mecánica revisa la batería = The mechanic checks the battery

If you said su batería, that would put more focus on whose battery it is, but it is not necessary here.

Because porque is the conjunction meaning because.

Compare:

• porque = because
• por qué = why
• el porqué = the reason

So in this sentence, porque introduces the reason:

• La mecánica revisa la batería porque el coche no quiere arrancar.
  = The mechanic checks the battery because the car won’t start.

Because this is natural Spain Spanish.

In Spain:

• coche = car

In many parts of Latin America, people more often say:

• carro
• auto

So el coche is a strong clue that the sentence is using Spanish from Spain.

This is a very common idiomatic use in Spanish. Machines and vehicles are sometimes described as if they had intentions.

So:

• el coche no quiere arrancar literally = the car doesn’t want to start
• natural English meaning = the car won’t start

It is a normal and natural way to speak in Spanish. A more direct version would be:

• el coche no arranca = the car doesn’t start / the car won’t start

Both are natural, but no quiere arrancar adds a slightly more expressive, everyday tone.

Quiere is the third person singular, present indicative of querer.

This verb is stem-changing:

• querer
• quiero
• quieres
• quiere

The e in the stem changes to ie in stressed forms.

In this sentence:

• el coche no quiere arrancar

the subject is el coche, so the verb must be quiere.

Because after a conjugated verb like querer, the next verb normally stays in the infinitive.

So:

• quiere arrancar = wants to start

That is the standard structure:

• querer + infinitive

Examples:

• Quiero comer. = I want to eat.
• Quiere salir. = He/She wants to leave.
• El coche no quiere arrancar. = The car won’t start.

You do not say quiere arranca.

In this context, arrancar means to start a vehicle or engine.

So:

• el coche arranca = the car starts
• el coche no arranca = the car doesn’t start

But arrancar has other meanings in other contexts, such as:

• to pull out
• to tear off
• to uproot

Context tells you which meaning is intended. With el coche, the meaning is clearly to start.

Because la batería is a thing, not a person.

The personal a is mainly used with specific human direct objects:

• Veo a María. = I see María.
• Escucho al profesor. = I listen to the teacher.

But with things, you normally do not use it:

• Revisa la batería. = She checks the battery.

So la batería is simply the direct object, with no a.

The accent marks show where the stress falls:

• mecánica = me-CÁ-ni-ca
• batería = ba-te-RÍ-a

They are written because without the accent marks, the normal Spanish stress rules would place the stress differently.

This is useful for pronunciation, especially because batería has a stressed í, which also helps show that the vowels are pronounced separately: rí-a.

Yes. Here are some common alternatives:

• La mecánica revisa la batería porque el coche no arranca.
• La mecánica está revisando la batería porque el coche no quiere arrancar.
• Como el coche no quiere arrancar, la mecánica revisa la batería.

These are all natural, but they differ slightly:

• no arranca is a bit more direct than no quiere arrancar
• está revisando emphasizes the action in progress
• como at the beginning also gives the reason, similar to since or as in English