Voltage fluctuations. - JeepForum.com
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post #1 of 6 Old 07-15-2020, 02:46 PM Thread Starter
lavendje
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Voltage fluctuations.

My 2007 JKU started having dramatic voltage fluctuations. It use to start with a 14.1 voltage steady maybe got to 14.2 but never drop below 14.1. Then around 2019 it started going crazy and starting at 12.9 or 12.8 then jumping to 14.1 and sometimes going up to 14.5. And now as the temp gets in the 97 to 98 during the day it drops to 13.2 and goes up to 14.4 as I drive. When I come to a stop it drops down to 13.2 or 13.3 then goes back to 13.5 or up to 13.8 And fluctuates in between there. Any idea what is going on? It is killing voltage alternator every few months. Someone said there are two voltage regulators controlling it, one in the alternator and one in the computer. Is this correct?


Last edited by lavendje; 07-16-2020 at 04:25 AM. Reason: Sentence incorrectly typed.
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post #2 of 6 Old 07-16-2020, 07:31 AM
cranbiz
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What condition is the battery in? The PCM senses battery state and commands the alternator to charge at the rate required to replenish the battery. If the battery has a cell bad or going bad, that couls explain the fluctuations. Also check your wiring for corrosion.
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06 KJ
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post #3 of 6 Old 07-16-2020, 11:34 AM Thread Starter
lavendje
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Itís a brand new battery. Could a higher amp battery cause this or battery type that could cause this? It has been happening ever since Iíve put a higher amp battery in it. Or could a faulty cable from the alternator to the battery cause this?
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post #4 of 6 Old 07-16-2020, 01:07 PM
cranbiz
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No, that shouldn't be the issue. I have a larger one in mine.

A faulty cable could certainly do it. Do you have any additional wires on the battery clamp nuts?

It's interesting that this is happening since replacing the battery. The design of the stock Mopar battery clamp is such that if the cone shaped nut that closes the clamp is compromised (by other added wires or if you replace the nut with a flat nut), it won't tighten the clamp properly. That will cause the issues you are seeing.

06 KJ
12 JK, 2.5" Teraflex lift, Bilstein 5100's, BFG KM3's 37x12.5/R17
17 WK2 Trailhawk
KN4BBA
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post #5 of 6 Old 07-22-2020, 03:36 PM Thread Starter
lavendje
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Well I hope the photo uploads to this forum. It should show the battery and the connection to see if there is anything wrong with it.
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post #6 of 6 Old 07-23-2020, 08:27 AM
cranbiz
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OK, not the clamps I was expecting but those are fine and won't have the issue with the cone nut.

Anyways, the green wire should be a fusable link that goes to the alternator and the TIPM. Thoroughly clean all connections at the battery clamp and then follow the green wire. Make sure it's solid and the connection at the other end is clean.

You may want to disconnect that smaller red wire to troubleshoot.

06 KJ
12 JK, 2.5" Teraflex lift, Bilstein 5100's, BFG KM3's 37x12.5/R17
17 WK2 Trailhawk
KN4BBA
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