When I turn the engine off, a small fan stays on, causing the battery to die. But it's not the radiator fans. I've switched relays of similar kind for the fans and AC and it still stays on.
My car has 167000 miles.
My car has an automatic transmission.
Hi, thanks for writing in. The noise you are hearing is the emission control system performing a system test of the fuel tank vapor system. The system should run the test in less than ten minutes. If the battery cannot last long enough to finish the test before it dies then the battery may be bad and cannot handle the load and needs replaced. Have the battery tested to make sure it is not bad. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.