i just bought a 99 expedition. while the engine is running all lights blink (interior, headlight, taillight, and dash light) when not running the lights are solid. removed the neg batt post and truck stayed running and lights went solid. should i replace the batt cables? what else could be wrong here?

 

First, you should not have removed the cable from the battery while the engine is running. The computers do not like that. To me it sounds like you have a problem in the voltage regulator. Cleaning the cables can't hurt anything and may actually help. The charging system needs load tested to see where the problem actually is. My best guess is alternator. Good luck.