Nissan Xterra

2002 Nissan Xterra Electrical / Lighting Systems Won't Start  

My xterra all sudden did not want to start. I check the battery and the positive terminal was decomposing. I replaced the part and bought a new battery from the nissan dealer ship. within 24 hours I went about 15 miles then stop at a store. when I tried to start the motor is did the same thing it didnt start. I had to jump the battery and drive home...what should I check and do to keep my xterra running well

Did you replace the positive terminal or the complete postive cable? It is very possible the corrosion bled down the cable making it to weak to function properly.

Is the alternator charging? If not the battery/charge indicator light should turn on alerting you of the problem. Chain autoparts store will check your charging system in the parking lot free of charge.

Let me know what you find and we'll go further if necessary.

2000 Nissan Xterra Heating / Cooling System Malfunction  

Fan does not engage (heat, air or a/c) unless on setting 4. A/C engages fine when 1-4, yet doesn't blow unless on 4, or on highway where speed is pushing air through system.

This sounds like classic symptoms of blower motor resistor failure. The resistor control fan speed (voltage) on all ON settings except high, in which case the resistors are bypassed.