Is want an auxiliary verb or main verb?

Hiya,

'want' would be a main verb as it is virtually impossible for an auxiliary to stand alone. Auxiliaries must always occur with a main verb, but main verbs can stand alone.

In English, there are both modal and tensed auxiliaries which are listed here for you.
Tensed:
has/had, is/was, are/were, does/did
Modal:
can/could, may/might, will/would, shall/should, must, ought

Take for example the sentence
i.e: I want the hamburger.
By substituting with other main verbs,
i.e: I love/ate the hamburger.
would be appropriate. If 'want' is an auxiliary verb, then it is supposed to occur with a main verb, which would be ungrammatical as seen below:
i.e:* I want decided to work here.
in comparison to
i.e: I have decided to work here.
where 'have' is an auxiliary.

Only tensed auxiliaries have the dual relationship of being either a main verb or an auxiliary as seen below:
i.e: It is very peaceful here.
where the above 'is' is a main verb and
i.e: The police is investigating the crime scene.
where 'is' is an auxiliary being accompanied by the main verb 'investigating'.

I hope the above explanation clears your doubt.