Possible Grounding Problem - Rubicon Owners Forum
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post #1 of 28 (permalink) Old 08-09-2019, 04:06 PM Thread Starter
Rubi Noobie
 
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Possible Grounding Problem

Hey guys. A recent project (audio install) has got me trying to figure out whether or not I have a poor ground somewhere.

Here are the two things that I have seen/noticed:

- When starting the engine, I'm seeing the voltage drop as low as 10.5 volts before climbing back up and spiking at 15 volts before falling back down to 14.7 - 14.9.

- I haven't been able to test this one with the multimeter, but I have been noticing what feels like another voltage drop when the Jeep is coming to a stop. Occasionally, it will lead to a rough idle, almost as if it's about to stall.

I've checked my connections at the battery and alternator. Both are great. I plan to check the ground connection on the engine block tonight, but that's as far as I've gotten. Does this sound like a grounding issue or something else?
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post #2 of 28 (permalink) Old 08-09-2019, 04:36 PM
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You may want to check for any DTC's
The charge rate of the alternator is managed by the PCM based on various inputs.
You could have a DTC stored that is not severe enough to illuminate the light in the dash.
Here are other things to check:
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post #3 of 28 (permalink) Old 08-09-2019, 10:01 PM Thread Starter
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Quote:
Originally Posted by FLLJ View Post
You may want to check for any DTC's
The charge rate of the alternator is managed by the PCM based on various inputs.
You could have a DTC stored that is not severe enough to illuminate the light in the dash.
Here are other things to check:
Just checked and it's not flagging anything.
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post #4 of 28 (permalink) Old 08-10-2019, 09:11 AM
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failing rectifier bridge in the alternator?
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post #5 of 28 (permalink) Old 08-13-2019, 12:44 AM
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Do you have another battery you can test with ? My TJ would have a hard time idling with a "shot" battery. Shot meaning a failing cell, if driven regularly you can get it to start (in the summer at least) but the charging system can't deal with it.
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post #6 of 28 (permalink) Old 08-13-2019, 08:52 AM
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Pull the battery and get it load tested.

John - WB5THT
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post #7 of 28 (permalink) Old 08-14-2019, 04:49 PM Thread Starter
Rubi Noobie
 
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Quote:
Originally Posted by Mouse View Post
failing rectifier bridge in the alternator?
I'm not 100% up on my game when it comes to automotive mechanics , so the rectifier being a potential problem, I'm not sure of, but I will look into this or open it up and take a look. Any suggestions on how I need to go about testing for this?

If this does happen to be the case, would it be something that I can just order up a diode and solder the new one in? Aside from that, I'm guessing I'd have to buy a whole new alternator, correct?

Last edited by Firemedic82; 08-14-2019 at 05:02 PM.
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post #8 of 28 (permalink) Old 08-14-2019, 04:56 PM Thread Starter
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As far as the battery, I'm not sure if a cell has crapped out on me or not. I (ignorantly) didn't think too much about the battery since it is only about a year and a half old, but we all know where assuming can lead us. I haven't been able to do any testing on it yet, but I will check the battery when I do get to it.

My gut is telling me the "voltage regulator" (if that's even what it's actually called), is failing on me, but ruling out these other potential suspects before I order up an external regulator. To my surprise, it really isn't too expensive though, which is a good thing. Far better than the price for a PCM I'm sure.

Last edited by Firemedic82; 08-14-2019 at 05:01 PM.
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post #9 of 28 (permalink) Old 08-14-2019, 04:58 PM Thread Starter
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I did forget to mention that I have now checked the engine block and chassis ground. Still need to do a voltage drop test on the others.
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post #10 of 28 (permalink) Old 08-15-2019, 08:38 AM
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Back to the original problem - did this all of a sudden start after you did something? You're assuming an idling problem is battery related? Did you load test the battery?

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