What's the plural of faulty? [closed]

The English you are suggesting would not be correct Fault has a plural (faults) as it is a noun. Faulty is an adjective which has no plural.

English does not inflect adjectives for case, number or gender agreement with the nouns they modify. Inflection Rules English does inflect nouns and pronouns (for number, not case or gender). However there are some examples of plural nouns which are being used as adjectives and still keeping the plural form. see Note

The car has one fault. The truck has two faults. They were both faulty when I bought them.

The car has one fault(noun). The truck has two faults(noun). They were both faulty (adjective) when I bought them.

fault noun Cambridge English Dictionary a broken part or weakness in a machine or system:

The car has a serious design fault.

faulty adjective Cambridge English Dictionary A faulty machine or device is not perfectly made or does not work correctly:

His arguments were based on faulty reasoning.

Note

Adjectives in English do not change (agree) with the noun that they modify: Cambridge English Dictionary

The tropical birds were beautiful. Not: The tropical birds were beautifuls.

plural nouns often act as adjectives, as in these examples: M W Learners Dictionary

Teachers unions

Girls hockey

Nurses station