So I recently bought a 2008 f150 Lariat and it seems to have a few electrical issues. I was wondering if anyone has a diagram. For the high beams to my dashboard? The low beams work fine but the high beam switch won't engage the high beams all the time?
Also my truck keeps saying charging system failed and the battery voltage meter is almost all the way down but the truck still run fine? thank you in advance

 

pull your codes, then clear the codes.

disconnect battery, remove/clean/tighten grounds and also the terminals/cables at battery (best to do this to all grounds, but especially the ones in kick panels in cab).

go have your batt and alternator tested at an auto parts store (typically free).

then test drive it again, and check codes.

report back with details.

 

. Before I took the battery in I noticed the battery voltage gauge in the dashboard was normal but when I parked it it was almost all the way down. I took the battery in to have it charged but immediately the charging system failed light came on?

 

this didn’t address a single item in post #2.

 

Codes are clear, grounds and terminals are cleaned, fuses are checked. Battery was tested and charged it's good. Maybe wiring issues?

 

- which grounds did you check and what did you do to check them ?

- was battery load tested?

- still no mention of alternator