Car won't start. no codes. i can jump it and it runs about 3 weeks. I changed
out battery , same thing. I changed alternator 3 years ago. car has aunder
Either you don't drive the car long enough to recharge the battery properly, or you have a battery drain within one of thee car's systems. If you drive short distances regularly, add a battery tender to keep up the charge. They are little battery chargers and aren't expensive. Otherwise have a mechanic track down the cause of the battery drain. Might be a defective electrical switch of a shorted-out wire.