Symptoms of a Bad Jeep Grand Cherokee Alternator
While your battery stores up the electricity your Jeep needs to start up and keep running, your alternator actually powers all the electrical parts of your Wrangler. You need to know how to diagnose any suspicious signs that you notice in relation to this component. Otherwise, it will be difficult, uncomfortable, or downright impossible to ride your Grand Cherokee.
You need to be aware of any suspicious noises that you hear while driving your Jeep because these are often the first signs of serious trouble. If you notice noises coming from your alternator, it could mean that you've got a bent pulley system, shortened diodes, or mechanical interference on your hands.
Dying electrical parts
A bad alternator will make its presence felt when your Jeep's electrical parts stop working. Your dashboard lights might dim, the radio might cut out, the heater or air conditioning might turn off, and ultimately, your engine might die. These are all signs of a faulty alternator. If you start experiencing this while you're miles away from any service station, then you'll need to turn off any electrical component that isn't necessary (such as the radio or the air conditioner) until you reach your destination.
Off-the-mark load test results
To test a Jeep Grand Cherokee alternator, you'll need to attach a voltmeter to your battery. First, you'll need to connect the positive and negative leads of the voltmeter with the corresponding battery posts. Then, take note of the battery's voltage reading on the voltmeter's display. If you see a reading other than what's within the range of 12.5 to 12.8 volts, then your battery is malfunctioning. If the reading falls within this healthy range, then have a friend start up your Jeep while you check the voltmeter. The numbers on its display will reflect the how much charge the alternator sends to the battery. If this reads anything other than what's within the range of 13.6 to 14.3 volts, then you have a faulty alternator.
Check gauge light comes on while electrical equipment still works
You might find it surprising that the check gauge sign lights up on your dashboard despite the fact that your air conditioning, lights, radio, and other electrical parts are functioning fine. You'll need to diagnose this with an alternator tester. The likely cause of this issue is a bad diode.