My 2000 Jeep Grand Cherokee wont hold a charge and needs to be jumped. When trying to start it makes a clicking noise and the console instruments jump. Is this the battery??? Or the alternator?? Or something else.?

When these vehicles and other brands get a 100k miles or more a dead battery can be caused by worn brushes in the alternator. I've found this problem in Toyota , Jeep , and Ford. There are two wires on the back of the jeep alternator that furnish Voltage to the field. You can lightly skin the insulation on these wires and connect a voltmeter. with the car running there should be approx 5 to 12 volts on these wires.If there is voltage on these two wires the battery voltage should be close to 14 volts. If the battery voltage is below 12volts and slowly dropping . You will then turn off the engine and disconnect the battery . Next remove the alternator. On the back of the alternator there is a thin plate . Remove this plate by removing three nuts, a ***** with a metal tab, battery connection nuts and insulator. the plate should come off. In the center of the alternator there is a brush holder held on with three Phillips head screws.Remove the screws and brush holder. If this is the problem you will notice copper filings and carbon buildup on the slip rings. Hold sand paper against the slip rings and turn the pulley on the front of the alternator by hand This will clean the slip rings. Buy and install a new brush holder with brushes.Put the alternator back together and on the car. Reconnect battery and check the voltage with the vehicle running. Hopefully this fixes your problem. With vehicles other than this model jeep the voltage regulator may be mounted on the alternator. There will usually be more than two wires on the back. Also if you don't need to save money you can buy a new alternator.

First remove and clean battery cables and battery posts with a wire brush or sand paper. Make sure battery is charged and check to see if it starts. Then check battery condition and charging system. The problem could be cables, battery, or alternator. Check them in order and repair or replace as needed. Check cables, battery, belts(tension and condition), and charging system in order. Do this because bad cables will give false readings for other tests and so on.

All cars do that when the battery is dead,or weak
all modern cars.
the battery can be weak for many reasons.
1: its bad. (battery) (or battery lugs green with corrosion)
2: charge system, failures. 13.3v to 15v running, not less.
3: lights left on or phantom drains in car,?
"hint, battery drains, parked" as you sleep. is big clue.

when you stated the car (jump) did the battery meter show 14v
or charge light to out?
and when ran it for long time 1hr. did it restart?
tell what happened after the jump and win.