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The battery is still good and the motor will keep running when you disconnect a terminal. Can my alternator be bad? If not I'm also thinking a dead short? What is the best way to find out?

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  • Is this a gasoline or diesel fueled vehicle?
    – James Jenkins
    Mar 16, 2014 at 9:53

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Sounds to me like you are not making connection to the battery (maybe this is what you mean by "dead short"?). I would look at your contact points ... both sides of the battery, ground, and starter to ensure you are making good contact. If you have side posts (assuming you do), these have a tendency of not making complete contact even when tightened. Make sure there isn't any rust or corrosion at the ground point causing interference. If you can disconnect a terminal, the alternator is still putting out juice. You can also put a multi-meter on it to test its output.

Also, when you say the battery is dead, do you mean you turn the ignition off, then go to turn it back on and ... nothing? Or does your dome light/radio turn on? Do accessories die when you turn the key or dead from the start? If you have dome lights which die when you turn the key, it's the connection at the battery as described above. If you turn the key, still have dome lights and nothing happens, it could be your starter solenoid or your ignition switch.

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  • It is worth noting, that are two Diesel engine options for this vehicle. Disconnecting the battery is may not be diagnostically accurate.
    – James Jenkins
    Mar 16, 2014 at 9:52
  • The 89 only had one Diesel engine available to it, but I am unsure what that has to do with the problem at hand?
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 16, 2014 at 12:40
  • Standing corrected, one diesel available. The OP is testing the alternator by disconnecting the battery. To the best of my knowledge this is only effective on gas engines.
    – James Jenkins
    Mar 16, 2014 at 21:29
  • @JamesJenkins ... I actually missed that when I answered this post. Thanks for bringing it to light. I'm not sure what method they used for shutdown of the diesel engine used in the 89 Cherokee. If there is a fuel shut off solenoid, where the solenoid is off when power is disengaged, this could have tested the alternator as well. Without some sort of shutoff like this, the possibility of a runaway is a lot greater.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 16, 2014 at 21:38

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