98 Honda Accord showing all doors open dash light

I'm a first time post. I have a 98 Honda Accord in pretty good shape even though it has 340,000 miles on it. For the past month I have intermittently been having the dash idiot light that shows all 4 doors and the trunk lid is open -- coming on. In addition, the "brake" light that is just to the right of the blue "high beam" dash light, also comes on and the past week the "battery" light comes on. It also seems like the headlights slightly dim and maybe even the blower motor slows down just little. It started out lasting less than a second and now last maybe 2 or 3 seconds. I took it by one of the Advanced Auto parts stores and they did a diagnose check on the alternator, starter and battery. Everything at that moment, checked out fine. Alternator checked out good during regular operation and under loaded condition. Almost everything on the car is original except timing belt. Anybody experienced this one? Thanks

I still would check the charging system!

The battery suppose to read around 12.6 volts with the key off and around 13.6 when running.

Make sure the battery terminal connectors do not have any corrosion signs on them (white residue). Try to wiggle the cables.

It could be a bad ground connection.

Good luck,
Sam

Thanks Sam,
Tomorrow is my day off, so I will check cleanliness and tightness of the battery connections then. I also want to find the diagnostic print out from Advanced Auto so I can share the alternator output voltages for both normal and loaded, as well as battery cold crank test results, and the starter draw while cranking. Intermittent problems are the worst. It did it one time on the way home from work tonight and lasted about 5 seconds. That is the longest ever yet. I agree the charging system sounds very suspect, even though it performed very well on the parts store diagnostic test.