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Battery Gauge Drops (Check Gauges)

T

TuXJ98

NAXJA Forum User
Location
Rancho Cucamonga, CA
I replaced my power steering pump, and experienced a strange thing during the test drive afterward.

Jeep drives fine, then randomly the battery gauge drops to almost zero and the “Check Gauges” light comes on. If I kill the engine then turn key back to on, the battery gauge goes back up to normal. I can drive for a couple minutes, then it repeats.

My OBD reader says 10.9v when the gauge drops to zero.

Anybody experience this in their Jeep? What did you find out? Could it be an alternator issue? One thing after another with these Jeeps I swear. just wish it could have at least given me a day between issues. [emoji2957]

https://youtube.com/shorts/8hVRWfML3gs?feature=share


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Are you sure the fan belt has proper tension ?

Excessively low battery voltage symptoms as described, are typically from a faulty alternator. Usually the brushes are worn.

Excessively high battery voltage displayed on the voltage gauge is typically from loose, dirty, or corroded connections and/or wires.
 
Last night I drove for a while and was watching the voltage on the OBD scan tool slowly fall. Don’t know if it’s accurate but it went down to 9.8v with headlights on. I pulled the alternator. Part number looks to be a new (not Remanufactured) Napa alternator, dated 2015.

I had it tested at Autozone since they were still open, he said he tested it three times and it passed. So I suspect a wiring issue that is preventing the alternator from charging.

Interestingly, I checked the battery (nearly brand new AGM battery) off the Jeep this morning with a meter and it read 11.8v on the meter.

I’m thinking of replacing the wiring with the Big7 set from Jeepcables.com to hopefully fix the issue. I read that there’s a fusible link by the fuse box going to the alternator. I’ll look up how to test that, although that would be replaced with the wiring kit.


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I would get the battery charged and load test it also
 
I have the battery on a charger now. I actually just bought it when this first happened this weekend, thinking my old battery gave up. Maybe new battery didn’t have a full charge when I installed it?

I just put a meter on the alternator line with the fusible link and have continuity. See photo.

f0d8e45d775afa2383604754c3dbd48e.jpg



Does anyone know if this piece that attaches to the two small terminals of the alternator are a sort of fuse that may be the issue?

03b137c09075fc26e4e4f60416802490.jpg



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Tim_MN said:
Are you sure the fan belt has proper tension ?

Excessively low battery voltage symptoms as described, are typically from a faulty alternator. Usually the brushes are worn.

Excessively high battery voltage displayed on the voltage gauge is typically from loose, dirty, or corroded connections and/or wires.
Click to expand...


I got the tension about where it usually is by feel. I didn’t dial it in exactly with my Cricket tool though. Pulley was spinning.


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grantb said:
Do you have a multimeter? Can you measure the battery voltage directly?
Click to expand...


Once battery is done charging and I get alternator back in, I’ll take some readings with the meter with the car running. Wish I would have thought to do that before disassembly. 😆


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Looking through my 1997 service manual, I think the piece with two terminals is just a connector - nothing special. The terminals are called "field terminals" and one should be 12v constant, and the other one varies.
 
Check the brushes.

The brushes wear down, and the springs loose tension. The brushes will push back, and get stuck. A bump in the road, turning the motor off, or removing the alternator will often free the brushes.

Showing 9 ish volts 98.7% of the time means the brushes are toasted.
 
Tim_MN said:
Check the brushes. The brushes wear down, and the springs loose tension. The brushes will push back, and get stuck. A bump in the road, turning the motor off, or removing the alternator will often free the brushes.

Showing 9 ish volts 98.7% of the time means the brushes are toasted.
Click to expand...


Thank Tim, can you elaborate on how I check the brushes since that is new to me?

Any wagers that if I just reinstall the alternator and charged battery, all will be working as it should? 😂

It was odd to me that before the steering pump job, I never had any electrical issues. Fired right up, even cold. Only thing I could think of that may have disturbed something was the bleeding process. I pulled the center wire of the distributor and cranked the started a few times while turning the wheel lock to lock to bleed air. Besides that, I don’t see how the two could be related except installing the belt incorrectly. But I triple checked the belt routing.


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TuXJ98 said:
I have the battery on a charger now. I actually just bought it when this first happened this weekend,
Click to expand...

For a new battery that voltage is a bad sign for the battery, like I said charge it and load test it. What brand is it?
 
Swap in a KNOWN GOOD battery, and restart your diagnostics from there.
TuXJ98 said:
One thing after another with these Jeeps I swear. just wish it could have at least given me a day between issues. [emoji2957]
Click to expand...

Maybe a 20-25 year old vehicle isn’t for you…?
 
I had my new battery load tested and had alternator tested again at a different location. Both tested good.

I’ll get it back together and see how it goes. This time if that gauge drops again, I’ll check voltage directly from the battery. 🤞


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Original alternator back in. I put a meter on the battery and watched voltage rise when the Jeep started. Went for an hour long cruise, with no issues. Alternator is charging, and battery is voltage is holding.


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I discovered a new gremlin today, that may become its own thread after doing some more research and troubleshooting first.

AC compressor and fan both don’t turn on at all now. I used the AC regularly and was fine up until the recent alternator/battery problem. Checked fan and AC fuses and they’re good. Any ideas welcome. Haven’t had time to check wiring for power yet.

At least it’s drivable again, so I’m thankful for that!
 
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