Here's how to troubleshoot this:
1. Verify the New Battery is Good:
* Load Test: Take the new battery to an auto parts store and have them perform a load test. This checks its actual cranking ability and ensures it's not defective. A bad new battery is possible, though less likely than a drain.
2. Locate the Parasitic Drain:
This requires a multimeter capable of measuring current (amps). Here's the process:
* Disconnect the Negative Terminal: Disconnect the negative (-) battery cable.
* Connect the Multimeter: Set your multimeter to measure DC amps (usually indicated by "A" with a symbol resembling a "~"). Connect the positive lead of the multimeter to the negative battery terminal. Connect the negative lead of the multimeter to the negative battery cable (where you just disconnected it). The multimeter should now show a current reading.
* Identify the Drain: The multimeter will show a small current draw (milliamps, mA). A perfectly normal draw should be under 50 mA. Anything significantly higher indicates a parasitic drain. To find the source, systematically remove fuses one by one (starting with the larger ones, then smaller ones), rechecking the amperage reading after each removal. When the amperage drops significantly, the fuse you just removed protects the circuit with the drain. Refer to your owner's manual to identify the circuit related to that fuse.
Common Culprits:
* Interior Lights: A faulty door switch, dome light switch, or trunk light switch can keep a light on even when the car is off.
* Radio/Stereo: The aftermarket radio may be drawing excessive power, or it might not be fully turning off.
* Alarm System: A malfunctioning alarm system is a common culprit for significant parasitic drain.
* Computer Modules: A faulty module or a short in its wiring can cause a constant drain.
* Alternator: While unlikely to cause a *complete* discharge in two weeks, a failing alternator may not be fully charging the battery. You can test the alternator's output voltage with the multimeter.
* Wiring Shorts: These are difficult to locate, but often result in a substantial parasitic drain.
3. Additional Tips:
* Clean Battery Terminals: Make sure the battery terminals are clean and tight. Corrosion can increase resistance and affect the charging/discharging process.
* Check the Battery Cables: Inspect the battery cables for any damage or fraying.
If you're not comfortable with electrical work, take your Grand Cherokee to a qualified mechanic. They have the tools and expertise to diagnose and repair the parasitic drain efficiently. Ignoring this problem will continue to damage your new battery and potentially lead to other electrical problems.
