Why are my dash instruments pegging out upon startup. The speedometer and tach go all the way to max and then fall back to 0. I have a 2003 F-150 supercrew with 4.6 automatic 2 wheel drive. I have never changed the battery and it does seem to be getting weak. Sometimes the doors will lock automatically when starting. The truck has 104000 miles on it. Everything seems to work on the truck it just does this instrument thing when started after sitting a while.