The gauges are stepper motors with pointers, not the older reliable mechanical gauges. The armatures are positioned by the computer pulsing four coils with varying voltages and polarities. When you reconnected the battery, there likely was a current surge or spike that sent those gauges up for an instant. When you turned on the ignition switch, the computer sets them to the desired position, and in the case of the speedometer, that's 0 mph. Regardless where the pointer jumped to, the armature looks for the shortest way back to 0 mph, and that could be clockwise. Unfortunately there's a stop peg in the way so the gauge can't move up from there.
The first thing to try is driving the car faster than half scale of the speedometer. Once you're going fast enough that the pointer's shortest way to the actual speed is to go counter-clockwise, it will jump there, then follow vehicle speed back down like normal.
You may be able to reset the fuel gauge by filling the gas tank so again, the shortest way to pointing to "full" is to go counter-clockwise. If those tricks don't work, you can use a scanner to run the gauge test sequence. That will make them all go to 1/4, 1/2, 3/4, and full scale, then back down. Once a pointer finds it needs to go counter-clockwise for the shortest way to get to where it wants to be, it will go there, then be in sync.
The third way is to remove any trim bezels, then the clear face, then push the pointers to where they should be. After that they'll move properly to where the computer sets them.
Wednesday, August 26th, 2015 AT 11:10 PM