Tonight coming home from work, I noticed the voltage needle started bouncing up and down while stopped. I got home and played with it for a little bit. When I turn on the defroster, the voltage needle drops to just about nothing. Turn it off and it goes back to center. I have just replaced the alternator about 200 miles ago. Any ideas where I can start. It has 208,000 miles. I have no clue when the plugs were changed, if ever.

 

It sounds like the alternator is going again. 200,000 miles is enough on those plugs and wires, you need to get those plugs out and wires changed. Check the battery and cables too.

 

First off like said above check batt and cables check conections on alt all grounds ect. Rember just because the alt is new does not mean it's good i know sad but true.

 

This week-end I am going to check the cables and the alternator. I drove the ranger to work Monday and could not get it to act up again. Drove like a champ.

 

check your starter power feed wire
there is second small power wire from the solenoid to the starter itself
( make sure the plastic coating is still intact )

i found that my problem was that very wire was badly corroded and grounding against the starter housing ( the insulation was completely melted away )