CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

2002 Ford Expedition drains battery but no problem found in shop!

My daughter has a 2002 Ford Expedition that would not start a few days ago. Her husband removed the battery and had it checked - it was bad and was replaced. The car started and worked fine for 2.5 days. Again, when she tried to start it, the engine would not turn over, the radio wouldn’t play, the locks wouldn’t work, but there was a clicking sound coming from under the dash. These were the same symptoms as the last time this happened.



Her husband removed the battery again, and it was found to be discharged at the repair shop. They charged it and he reinstalled the battery in the car, started it and drove it to the repair shop.



The mechanics at the repair shop found nothing wrong with the battery, alternator, or the electrical system, and told them to drive it again until the problem again occurred, and have the car towed to their shop!



Any thoughts on what could be causing this?

It’s probably a parasitic drain. This will most likely be from some electronic module that is going bad or from marginal (dirty) switch contacts in one of the door switches or similar.
The diagnostic steps to correctly find this are time consuming. Basically, you measure the current drain from the battery while the truck sits undisturbed with all doors closed. After thirty minutes or so, the drain should go below 50mA (0.05 Amps) and stay there. If it doesn’t, then disconnect modules one by one and repeat the test. If it does go to below 50mA, then the truck will have to sit overnight with the current monitored to see if some module is waking up at random and drawing excess current.

Thanks,I’ll relay this to her and let her discuss with the mechanic that seems to be totally puzzled about the situation!

I have the exact same problem with the same vehicle. I would like to know if this was resolved and how? Thanks.

You need to test for a parasitic current drain on the battery. Here is a link to refer to that explains the process.

https://www.aa1car.com/library/battery_runs_down.htm