carmaker vs car maker

carmaker and car maker both are nouns.

Word	Noun	Adjective	Verb	Adverb
carmaker	Yes	No	No	No
car maker	Yes	No	No	No

As nouns, carmaker and car maker are synonyms defined as:

carmaker and car maker: a business engaged in the manufacture of automobiles

Other synonyms of carmaker include auto maker, auto manufacturer, automaker, car manufacturer.

carmaker (noun)	car maker (noun)
a business engaged in the manufacture of automobiles	a business engaged in the manufacture of automobiles