You are in the right, he stated as-is...but that it lights up in "as-is" condition, you did not receive it in that condition.
I would threaten him with a negative if he gives you any more crap, don't yell and act pissed,just state the logical facts and say it is your only recourse since you cannot test that it "lights up" without the cord.....so how could you accept that he sold you the item as it was described?