2000 JCS no start, voltmeter high

Hi everybody! I know nothing about cars and have never been on a forum before, so we'll see how this goes!

I have a 2000 Jeep Cherokee Sport. Everything was fine until yesterday when I went out to start the car and it wouldn't start. Wouldn't even try, no lights, no sounds, nothing. Tried to jump it and the battery wouldn't hold the charge, wouldn't idle - would try to start but couldn't stay started. We got a new battery and it ran fine for a day and now the "check guages" light is on and the voltmeter is at 19 instead of the usual 13. What is most likely wrong and what is the cheapest way to fix it? I went on a long road trip last week and the air doesn't get cold so we had it on high, as cold as it would get for awhile, if that makes any difference...

Thanks!!!

Sounds like a voltage problem. Since you have a new battery, I'd think to check both the battery cables (which can be corroded on the inside although they look fine outside) and the alternator. The alternator can be checked at Autozone (or most auto parts stores) to see if it's putting out the correct amount of power. The cables can be checked at home by peeling back some of the insulation.

Possible bad ground or ground cable??

First tip, if there is a Jeep shop that is not a dealer, take it there.

The AC doesn't matter in this case...it is a separate issue...we can talk about that later.

I'm new to this also. Iam a student at wyotech for automotive try putting a multimeter on the batery set to volts. If it is overcharging it will read over 14.8volts. if that is the case check the big cable one the back ove hte alt. it should read 14.0-14.9.