The problem isn't that the calculators are wrong, says Mike Burgiss of Cox Automotive. Instead, customers "can enter any APR or loan term they want" and then be provided with erroneous information. For example, if someone enters 0% interest and the longest term length available (say, 84 months), they might receive a payment estimate of $250 from the dealership website calculator. Then, armed with this (incorrect) information, they proceed to the automobile dealership. At that point, it becomes Mr. Joe Salesman's issue to resolve, because the unhappy customer was expecting that brand new top-of-the-line, fully loaded deluxe edition for about half of what they will actually end up paying.
There are two possible solutions to this customer-unfriendly issue: first, take Mr. Burgiss's advice, and take the payment calculator off your dealership website. This would seem at first glance to be the quickest and most efficient way to deal with the issue. As an added bonus, it might provide the impetus for the customer to get up from their computer and make their way into your sales room. The second fix is to post a straightforward, prominently displayed disclaimer in close proximity to the online calculator. By taking this step, you could spare your salesperson the indignity of having to crush the customer's sweet-deal dreams.