Learn Swedish: Denna fjärrstyrda bil är mindre bristfällig än vad kunden misstänkte. - This remote-controlled car is less flawed than what the customer suspected.

The phrase än vad translates to "than what". While you could grammatically just say än kunden misstänkte, adding vad acts as a placeholder for the degree of the flaw. It makes the comparison explicitly clear and is highly idiomatic in Swedish when comparing against a full clause containing a verb.

Could I use som instead of vad after än here?

No, som does not work here. The word som is a relative pronoun that refers back to a specific noun. In this comparative clause, you are not referring back to the car itself, but to the abstract degree of how flawed the customer thought it was. For abstract concepts or whole clauses in comparisons, Swedish requires vad.

Why is bil in the indefinite form when the adjective fjärrstyrda has the definite -a ending?

The formal demonstrative pronoun denna causes this specific pattern. Words like denna, detta, and dessa require the noun to be indefinite (bil). However, they still force the adjective into its weak form, which takes the -a ending (fjärrstyrda). If you used the more conversational den här, the noun would be definite: den här fjärrstyrda bilen.

How is the word bristfällig constructed?