One of the most vulnerable points in 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 in 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 does not respond correctly to its commands. The second indication will be a voltage drop.
To replace the alternator:
1. Remove the battery and battery tray.
2. Remove the air box and loosen the power steering pump bolts to loosen the belt. It is not absolutely necessary to loosen the belt to reinstall the alternator, but it does make it feel a lot easier.
3. Working from under the Jeep, remove the main power cable from the alternator. This will be the large wire with a cover over the bolt.
4. Next, remove the control cables. On some older models these are held in place by a somewhat unusual 7mm bolt. There are four bots in total that keep this connection in place.
5. Now working from the top, remove the top and bottom mounting bolts.
6. Note the stamped steel brace at 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 gain clearance to reinstall the new alternator.
7. To remove the alternator from the engine compartment, you will probably have to lift the engine slightly. The easiest way to do this is with a jack under the engine oil pan. Be sure to distribute the load with a block of wood to avoid damaging the sump.
8. You can also have the AC lines bent slightly if they interfere with removal of the alternator.
9. Install the new alternator in place.
10. Put the motor back in place and reinstall the mounting bolts.
11. Tighten the bolt next to the mounting bolt if it was loosened earlier.
12. Replace the control wiring harness.
13. Replace the main cable. And put the cover back on.
14. Tighten the belt.
15. Tighten power steering bolts and replace air box.
16. Remove any keys you have left lying around.
17. Reinstall the battery tray, reconnect the battery and test it.
18. The check engine light should go out immediately and the battery voltage should begin to rise.
Note that if you allowed the battery to discharge before replacing the alternator, it’s a good idea to charge the battery from a different source before installing a new alternator. A new alternator can be permanently damaged if a high load is applied to it at its initial startup.