אתמול הייתה תקלה במזגן, ולכן התקשרתי למוקד של החברה.

That is true in the present tense:

• יש תקלה במזגן = There is a malfunction in the air conditioner

But in the past tense, Hebrew usually uses forms of היה:

• הייתה תקלה במזגן = There was a malfunction in the air conditioner

So in this sentence, הייתה is the normal way to say there was.

Because תקלה is a feminine singular noun.

Hebrew past-tense forms of היה agree in gender and number with the noun that follows in this kind of sentence:

• היה = masculine singular
• הייתה = feminine singular
• היו = plural

So:

• הייתה תקלה = There was a malfunction
• היה עיכוב = There was a delay
• היו בעיות = There were problems

תקלה usually means a malfunction, fault, technical problem, or breakdown.

It is more specific than a very general word like בעיה (problem). With a machine or device, תקלה sounds very natural.

So תקלה במזגן suggests that the air conditioner was not working properly, had a fault, or broke down.

Hebrew often puts time expressions near the beginning of the sentence, especially when setting the scene.

So:

• אתמול הייתה תקלה במזגן... = Yesterday there was a malfunction in the air conditioner...

This is very natural Hebrew word order.

You could move אתמול later, but the original version sounds smoother and more typical in everyday narration.

Because the preposition ב־ (in / at / with) combines with the definite article ה־ (the).

So:

• ב + המזגן becomes במזגן

This kind of contraction is very common in Hebrew:

• ב + הבית → בבית
• ל + המוקד → למוקד
• כ + הספר → כספר in theory, though with common words you usually see the normal contracted written form in context

In your sentence, במזגן means in the air conditioner or more naturally with the air conditioner.

Yes, literally it is in the air conditioner, but the natural meaning is more like:

• with the air conditioner
• in the AC unit
• affecting the air conditioner

Hebrew often uses ב־ in places where English would choose a different preposition. So this is a normal Hebrew way to talk about a fault in a device.

ולכן means and therefore, and so, or simply so.

It is made of:

• ו־ = and
• לכן = therefore / so

In this sentence:

• ולכן התקשרתי... = so I called...

It sounds a bit more formal or polished than very simple אז (so / then), but it is still perfectly normal and common.

התקשרתי means I called or I phoned.

It comes from the verb להתקשר = to call / to phone.

The ending ־תי marks I in the past tense:

• התקשרתי = I called
• התקשרת = you called (masculine singular)
• התקשרה = she called

Hebrew often leaves out the subject pronoun אני because the verb ending already tells you who did the action. So התקשרתי already means I called without needing אני.

Because להתקשר takes the preposition ל־.

So Hebrew says:

• התקשרתי למוקד = I called the call center
• literally, something like I phoned to the call center

You do not use את after להתקשר, because את marks a direct object, and this verb normally connects with ל־ instead.

In this sentence, מוקד means something like:

• call center
• service center
• hotline
• support center

The basic meaning of מוקד is center or focal point, but in customer-service contexts it often refers to a phone service center.

So מוקד של החברה is most naturally the company’s call center or the company’s service hotline.

Hebrew has two common ways to express possession:

1. X של Y = X of Y / Y’s X
2. A construct form, such as מוקד החברה

So these can both mean roughly the company’s call center:

• המוקד של החברה
• מוקד החברה

The של version is often clearer and very common in everyday Hebrew.

In your sentence, של החברה simply means of the company or the company’s.

Excellent question: in unpointed Hebrew spelling, למוקד can represent either:

• למוקד = to a call center
• למוקד = to the call center where ל־ has combined with ה־

The spelling is the same without vowel marks.

You usually tell from:

• context
• meaning
• sometimes pronunciation, if it is spoken rather than written

In this sentence, because it says של החברה, the intended meaning is naturally to the company’s call center, so definite English is the best translation.

Because Hebrew does not need subject pronouns as often as English does.

The verb form already tells you the subject:

• התקשרתי = I called

So adding אני would usually be for emphasis, contrast, or clarity:

• אני התקשרתי למוקד, לא הוא = I called the call center, not him

Without emphasis, leaving אני out is completely normal.