Something is not making sense on this. Is there a problem with paying off your trade in? Did the daeler learn something about the trade in after the deal was done that was not know when the deal was made? Have you been contacted by the bank which approved your financing? What is the delaer giving you as a reason for not doing the deal? You should contact as attorney to assist you if this is not resolved promptly between you and the dealer.
Often times car dealers have customers sign contracts and send the purchaser down the road with the car when financing has not fully been approved yet. Most banks are not open on the weekends and it may take a day or two to complete the financing. When dealers cannot get a customer approved at the rate in the original contract, they call and have the customer re-sign a new contract at a different rate. Dealers are required to get the financing completed within 4 calendar days exclusive of Saturday, Sunday, or legal holiday otherwise they may be subject to "bushing" laws which would be a violation of RCW 46.70.180 (4): "To commit, allow, or ratify any act of "bushing" which is defined as follows: Entering into a written contract, written purchase order or agreement, retail installment sales agreement, note and security agreement, or written lease agreement, hereinafter collectively referred to as contract or lease, signed by the prospective buyer or lessee of a vehicle, which: (a) Is subject to any conditions or the dealer's or his or her authorized representative's future acceptance, and the dealer fails or refuses within four calendar days, exclusive of Saturday, Sunday, or legal holiday, and prior to any further negotiations with said buyer or lessee to inform the buyer or lessee either: (i) That the dealer unconditionally accepts the contract or lease, having satisfied, removed, or waived all conditions to acceptance or performance, including, but not limited to, financing, assignment, or lease approval; or (ii) that the dealer rejects the contract or lease, thereby automatically voiding the contract or lease, as long as such voiding does not negate commercially reasonable contract or lease provisions pertaining to the return of the subject vehicle and any physical damage, excessive mileage after the demand for return of the vehicle, and attorneys' fees authorized by law, and tenders the refund of any initial payment or security made or given by the buyer or lessee, including, but not limited to, any down payment, and tenders return of the trade-in vehicle, key, other trade-in, or certificate of title to a trade-in. Tender may be conditioned on return of the subject vehicle if previously delivered to the buyer or lessee."
However, if they did attempt to contact you prior to 4 days after the contracts were signed, there might not be a "bushing" law violation. 3 weeks is a long time to not have gotten the financing completed. If there is a violation of the bushing laws, your rights are to be put back in the position you were in before you purchased the car - give you back your trade and any money you put down and you give them their car back. Or make them finance the deal to the terms of the contract.
You should contact an attorney who can review all of the paperwork your were given by the dealership and investigate why it took so long for the dealership to contact you.
This information does not create an attorney-client relationship nor does it constitute legal advice. Evaluate this information and independently decide how to proceed. Consult an attorney who practices in the county in question.