I have an '06 Freestar SE 3.9L, it has 92000 miles. Recently all the lights have started flickering. Never shutting off, but like a fast flicker. I have had the electrical system extensively diagnosed by both independent shops and dealers. It seams everyone just wants to replace parts rather than track down the issue.
Here's what has been done... New 65 EXT Motorcraft battery, new re manufactured alternator, new plugs, plug wires, coil pack (I had a misfire). It does have a remote start that was professionally installed 2 years ago. I did however disconnect it to see if that was it, and it was not. It is every light in the car, Dome, Dash and Exterior. I have tested the power coming into the headlight switch with a test light and the test light was flickering. So it is not the switch. The ford dealer cleaned all the grounds and there were no codes stored. These lights only flicker when the car is running. A note on the alternator, the old one tested fine but i had it replaced any way as a last ditch effort. No luck.... The dealer doesn't know whats going on, though I think the 15 year old they had working on it might not have the experience.
I do not have any modifications. Stock stereo, stock speakers. Everything in this car is stock. There is a iPhone interface that is spliced into the cigarette lighter power wires to charge my phone and play through the radio as it also broadcasts over FM. This has been there for about 1.5 years. I am baffled. Please help, any ideas would be greatly appreciated. I'm hoping for people who specialize in electrical diagnoses.