My son's 2wd, 3.0L Ranger started going dead and needing a jump. The dome light won't turn off and the "door ajar" light stays on.. We tried the "WD-40 in the door switch" trick to no avail. I pulled the lights out of the dome and it still needs a jump to start, even after a 15 mile highway drive to charge the battery.

There may be multiple issues, but I'm thinking it's the alternator.

During the 15 mile highway drive my son told me the radio cut out three times. I was behind him and his brake lights and turn signals appeared to glow brightly in the midday sun. Still, after parking his truck for about four hours it wouldn't even turn over.

The battery looked good. It's a Motorcraft battery about three years old, and the water level was good and the plates inside were perfect. This all started this morning so there hasn't been any equipment attached to the charging system to say for sure.

Could a faulty door sensor be the culprit, even though the three lights it would activate have been removed? That'd be a lot less money than an alternator.

Yes. The BCM thinks the door is open and won't go to sleep.
So there will still be a significant battery draw with the bulbs removed.

Interesting. Thanks. Those switches are cheaper than an alternator, so I really hope that's it.

Should be a simple switch. Should be able to un hook the switch and see if it fixes it before you spend money on parts.

You need to test the alternator before replacing it. When running the voltage should be 13.6 to 14.6.

If the alternator is good test the battery. Any parts store can test both for you for free.


Test don't shotgun the repair.

It was the battery after all. I bought a door switch anyhow, but the new battery solved the "not starting" problem.