One of the more vulnerable points on the otherwise very reliable Jeep Cherokee is the alternator. The alternator is located very low on the engine and is susceptible to damage from mud and water during off road conditions.
Usually the first indication of an alternator failure will be the check engine light. The ECU controls the alternator and will detect when it is not responding properly to its commands. The second indication will be a drop in voltage.
To replace the alternator:
1. Remove the battery and battery tray.
2. Remove the air box and loosen the bolts on the power steering pump to loosen the belt. It is not absolutely necessary to loosen the belt to reinstall the alternator but it make sit a lot easier.
3. Working from under the Jeep, remove the main power wire from the alternator. This will be the large wire with a cover over the bolt
4. Next remove the control wires. On some older models these are held in place by a somewhat unusual 7mm bolt. There are four bots total holding this connection in place.
5. Now, working from the top, remove the upper and lower mounting bolts.
6. Note the stamped steel stiffener on the front of the engine that the alternator bolts to. Loosen but do not remove the bolt next to the alternator bracket. This will help get space to reinstall the new alternator.
7. To get the alternator out of the engine bay, you will likely have to raise the engine slightly. The easiest way to do this is with a jack under the engine oil sump. Be sure to spread the load with a block of wood to avoid damage to the sump.
8. You may also have the slightly bend the AC lines if they interfere with removal of the alternator.
9. Install the new alternator in place.
10. Lower the engine back into place and reinstall the mounting bolts.
11. Tighten the bolt beside the mounting bolt if you loosened it earlier.
12. Replace the control wiring harness.
13. Replace the main wire. And reposition the cover.
14. Tighten the belt.
15. Tighten the power steering bolts and replace the air box.
16. Remove any wrenches that you may have left lying around.
17. Reinstall the battery tray and reconnect the battery and give it a test run.
18. The check engine light should be gone immediately and the battery voltage should begin to climb.
Note that if you allowed the battery to discharge before you replaced the alternator, it is a good idea to charge the battery from a different source before installing a new alternator. The new alternator can be permanently damaged by placing a high charging load on it at its initial startup.