Needle Bounce
Needle bounce:
Short answer: It's not you its one of the lovely tics of our beloved beasts. and that bouncing is letting you know that its doing its job and reading voltage draw/gain and how hard its working.
Redundant long answer: I remember when i first got my bronco ~6 years ago it did the same thing. There used to be a good thread on why it does it, dont know if its here anymore. All i know is that, like referenced in the old thread, mine is the same. The higher the direction of the bounce into either the positive or negative side, the more the battery is being charged or drained. Its easy to see once you know you have a good charged battery in there. watch it when everything is off, it should be bouncing close to the zero. Then, while at idle, start turning things on and you will see it go into the nagative farther with each accessory activated. Bring the rpms up and you will see it start to bounce (hopefully) into the positive side. My alternator has been "bad" ever since i got my ol bronc'. It doesnt really start charging until i get into the 2k rpm range (even then it is minimal-i seriously need a new starter, lol). With my highbeams, wipers, and radio on even at the higher RPMs on the autobahn or e-way it wont keep up, (the yellow top altima really pays for itself in this rare situation). The next morning i just drive in 2nd at town road speeds (with everything off) during my short drive to work and let her charge back up. Once i learned how to read and manage the voltage meter, i've never run my altima down again after the first year.
On the other ?:
If you dont already, you should always keep a spare voltage regulator, ignition control module, and starter solenoid with the required tools on hand (in the vehicle). They are notorous for going out at the worst times. I've had some last 2+years and other only last a few months. When i was stateside the guys at advance auto and auto zone were really good about honoring the warrenties the units come with.
As far as testing them, if i remember right, i think the spares from ac delco come with a wiring diagram and how to test the part on a piece of paper in the box. maybe others do as well.
I know my voltage regulator is going when the needle stops bouncing and stays flat or moves slowly instead of like its on speed.
When my ignition control module starts going my truck starts acting like it has a clogged fuel filter or like a cold carb in the winter. Then, it progress to cutting out in low power situations (ie, abruptly releasing the accelorator during aggressive maneuvers or coasting down a hill) and not wanting to restart for a bit afterward, eventually progessing to not starting at all. After checking my fuel filter, cap and rotor, ignition solenoid, and wires, it usually always is the module. (-funny, almost missed a new years eve hunt for this very reason yesterday. Cut out in the middle of nowhere halfway between my and my buddies place
)
The starter solenoid i've never had to replace on mine, but i've seen it happen to enough of my other bronco friends. it's a small part and easy to just add to the other two.
I've given more than one of these to bronco brothers when in need. ;D
A little long i know, Hope this helps though,