I work at an e-commerce company which sells replacement parts, we carry thousands of products which fall into several categories & subcategories and at the same time, fit different brand, model and version items.
Currently the only way for a user to find any part he needs is to provide the brand, model and version of the item he has using a set of selection boxes. After that, he is taken to a page with the list of all the categories, and then after clicking one of the categories, he sees a list of all the parts that match what he was looking for.
There is no other way to navigate the site, there is no link to the categories or subcategories on the home page.
Would this have any impact on the purchase decision of the users? Would the current navigation flow (via select boxes) give the users a "weird" experience and reduce the change that they place an order?