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My 1996 Jeep Grand Cherokee started beeping and telling me to check the battery. So I had the car tested and it said the voltage regulator was bad.

The voltage regulator on these Jeeps are in the PCM, so I had to bypass it with another external voltage regulator rather than replacing the $200 PCM.

Now that I have replaced the regulator, and gotten a new battery, the voltage gauge is going all over the place. But when tested, the battery is being charged by the alternator at a perfect amount.

Now overnight the battery is being drained somewhere and dying. I don't know if it could be the new external voltage regulator or a shortage.

  • youtube.com/watch?v=AvLbb48tQPw This isn't really an answer, but he pretty much explains diagnostics on that type of charging system. – cloudnyn3 Mar 20 '16 at 18:00
  • @OP, I've done the same thing on these Jeeps. The Voltage gauge would stop working because it received the signal from the PCM. The system would work perfectly, though. It seems you may have a bad regulator (they can sometimes be faulty) or a bad connection. Did you solder the wires or just twisted them together? – race fever Mar 20 '16 at 19:50
  • We used bullet connectors to connect to te new external regulator. When tested the regulator is putting out a perfect amount of power. The battery is draining overnight. We've decided that it has to come from the new part added in since this wasn't an issue before the new part. We are thinking of wiring the new regulator to an ignition switch so that it won't be able to drain power of the car is off. What is your opinion on this? Thanks! – Brady walling Mar 21 '16 at 1:00
  • Depending on the setup maybe a diode to limit flow direction would work as well. If you have a wiring diagram that would help. – Ben Mar 22 '16 at 21:17
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Certainly the issue would probably have to do with the last change made to the system. I'm sure this doesn't escape you.

You will need to test for parasitic drain if you want to nail the issue down. If you are unfamiliar with using a multimeter, here is a general howto on it's use and various functions.

Multimeter - Basic Functionality and Howto

Here is an QA on tracking down parasitic draw.

How to track down an intermittent battery drain?

A trick I used to use decades ago is mentioned in the article above. Use a flashlight bulb in between your battery and ground cable. If it lights up, you have some draw. A multimeter is much more precise though.

This certainly doesn't completely answer your question but I hope it assists you troubleshooting your issue.

Best of luck.

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Install a relay switch between the battery and voltage regulator and run the power wire to the relay through an accessory item like the radio so the regulator is only getting power when the ignition switch is on.. I just got through doing all of that on my 2003 dodge grand caravan

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