My 1999 F150 had a guage sweep problem on start up a few months ago, I replaced the battery and the problem went away. Now its doing it again, mostly if the truck hasn't been running for a few hours. any thought?

 

So what you saying is when you turn the key to start truck the dash gauges sweep all the way to one side and comes back?
If thats whats happen, it could be windshield leaking or moisture getting to where your computer is located, causing this problem.
That happen to my truck just recently, since my windshield was cracked I had it changed, solved my problem!

 

im gonna say ur battery is perfectly fine except for the fact that its not charged fully. however, it could be a lemon.

im going to suggest your alternator is bad, and because the battery was new it managed to keep the new battery decently charged for a while. but now the alternator cant keep up with the current draw, and isnt properly charging the battery.

try putting a battery charger on the battery, and get it fully charged while its sitting. then turn it over and see if they sweep. if it doesnt sweep after u charge the battery, the alternator is going out.

if youve never replaced the alternator, its probably time, it is going on a decade.

 

Put a battery charger on it to see what happens, but before I did I checked the voltage with my multimeter, it read 12.4

 

it should be reading in the range of 13.8/14v.

when u turn the truck over its probably dropping the voltage to around 11v (from 12.4), which is to low so get the sweep.