Charging problem. - JeepForum.com
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post #1 of 18 Old 06-15-2021, 02:24 PM Thread Starter
Kiwimg
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Charging problem.

I have a 2002 Jeep Grand Cherokee Ltd 4.7 AWD. I’ve got a problem that started out with the volts fluctuating between 13.9 and 12.5 then when I’ve driven for 5-10 minutes it’ll drop down to 12.5v and then just start draining the battery from there. So far I’ve replaced the battery, checked the alternator (properly by mechanic), and thinking that it’s the voltage regulator, the mechanic installed a by-pass/ external voltage regulator which didn’t work either. I’ve since supplied an ECU which hasn’t solved the problem either. I’ve got another ECU on the way in case I happened to get a bad one. Mechanic found a faulty battery temperature sensor which he’s also replaced and was confident that was going to be the problem; unfortunately it wasn’t. All ground wires have been checked, cleaned and replaced where necessary, and at this point we’re starting to run out of things it could be. Mechanic is saying the instrument cluster has been flashing on and off and at one point the screen turned blue as well. The next thing to look at is the wiring harness and instrument cluster which I know isn’t going to be cheap! The motor is new/rebuilt 15k miles ago and had been running fine, and the new ECU is a plug and play for the vin number on this Jeep. Any ideas or suggestions at this point will be greatly appreciated and will save me having to push this pos Jeep off a cliff and on fire 🔥 😂
TIA
Matt, Tri, Cadence, & Koru 🐾🐾🐾

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post #2 of 18 Old 06-15-2021, 02:44 PM
Double E
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"Mechanic is saying the instrument cluster has been flashing on and off and at one point the screen turned blue as well."

Screen? What screen are we referring to for that?

Instrument cluster flashing on and off...
You have analog gauges (with needles pointing across a sweep of a range), ...what exactly is flashing on and off?

"We have it totally under control. Itís one person coming in from China. We have it under control. Itís going to be just fine." ~D. Trump, Jan 22, 2020.
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post #3 of 18 Old 06-15-2021, 03:06 PM
jtec
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All you have to do is -
Answer Double E's questions -above.
Scan and post ALL codes - the alt field circuit will set codes. YES scan even if light is off.

This is a simple system, 3 wires, controlled by PCM.
Battery is how old? replaced may not be NEW.
ANy 3rd world modifications, add on's, changed from jeep components ?

ECU? the term PCM is more common. but we can adapt

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 18 Old 06-15-2021, 09:31 PM
WJ60
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Quote:
Originally Posted by Kiwimg View Post
when Iíve driven for 5-10 minutes itíll drop down to 12.5v and then just start draining the battery from there.

I know you said the alternator and voltage regulator were checked, but that is a classic symptom of a bad alternator, regulator, or wiring from the alternator to the battery.
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post #5 of 18 Old 06-16-2021, 04:17 AM
Delta0
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Quote:
Originally Posted by Kiwimg View Post
I have a 2002 Jeep Grand Cherokee Ltd 4.7 AWD. Iíve got a problem that started out with the volts fluctuating between 13.9 and 12.5 then when Iíve driven for 5-10 minutes itíll drop down to 12.5v Did you get that figure from a calibrated meter?
and then just start draining the battery from there. How do you know it's draining the battery?
So far Iíve replaced the battery, checked the alternator (properly by mechanic), and thinking that itís the voltage regulator, the mechanic installed a by-pass/ external voltage regulator which didnít work either Is it time to find yourself an auto-electrician?. Iíve since supplied an ECU which hasnít solved the problem either. Iíve got another ECU on the way in case I happened to get a bad one. Mechanic found a faulty battery temperature sensor which heís also replaced and was confident that was going to be the problem; unfortunately it wasnít. All ground wires have been checked, cleaned and replaced where necessary, and at this point weíre starting to run out of things it could be. Mechanic is saying the instrument cluster has been flashing on and off and at one point the screen turned blue as well. The next thing to look at is the wiring harness and instrument cluster which I know isnít going to be cheap! The motor is new/rebuilt 15k miles ago and had been running fine, and the new ECU is a plug and play It ain't necessarily so. for the vin number on this Jeep . Any ideas or suggestions What is your battery voltage after a trip?
You have to leave your car locked for the readings.
What is your battery voltage 24hrs after a trip?
What is your battery voltage 48hrs after a trip?
at this point will be greatly appreciated and will save me having to push this pos Jeep off a cliff and on fire 🔥 😂
TIA
Matt, Tri, Cadence, & Koru 🐾🐾🐾

Down Under Kiwi Dogs- kiwidogs.com
The WJ charging system is programmed to be just good enough.
Just good enough for Mr Average.

It sounds like your expectations may be out of kilter with Mr Av.

I suggest you find yourself an Auto Sparks.
One with a calibrated meter.
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post #6 of 18 Old 06-16-2021, 10:43 AM Thread Starter
Kiwimg
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I know the battery is draining because my Jeep won’t start. Yes to calibrated meter. I don’t know what the voltage is after 24-48 hours because the more I drive the Jeep, the battery will slowly drain (I have an aftermarket meter in the car), and I don’t want to get stranded. When it first happened, the battery got down to 9.5v and things like o drive stopped working.

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post #7 of 18 Old 06-16-2021, 10:49 AM Thread Starter
Kiwimg
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The battery is brand new with 3 year warranty, I had it replaced at auto zone when I limped in there on 9.5v. Not getting any codes on scan.
No modifications. Only thing I’ve done in the last year is replaced the engine which has been running on the original ECU/PCM for the last 15k miles.

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post #8 of 18 Old 06-16-2021, 10:52 AM Thread Starter
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The idiot lights on the instrument panel are flashing on and off (Jeep not running), and the screen that turns blue are those lights as well .

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post #9 of 18 Old 06-16-2021, 01:01 PM
jtec
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check the fusible link.
With eng off, what is the voltage on the large wire rear of alternator?

You used a scanner NOT the key on off trick?
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When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #10 of 18 Old 06-17-2021, 02:08 PM
Delta0
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Have I understood correctly?

1) Your meter says your alt is making 12.5v.
2) The same meter says your battery has only 9.5 volts.
3) You have a big fat cable connecting your alt to you battery.

I had a problem with charging that I solved by disconnecting, and reconnecting the connector at the back of the alternator a number of times.
Disconnecting and reconnecting cleans contacts.

You can test your alternator thus: -

Pull the connector at the back of the alt.
Connect the one of the connections at the back of the alt to your battery, and the other alt connector to the the other battery post.
And run the engine very briefly.
A good alt gives 16 - 17v
If you don't get 16-17v your alt is suspect.

2.5mm female blade connectors fit the males on the back of the alt.
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post #11 of 18 Old 06-17-2021, 02:23 PM
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How much current flows between battery post and detached battery cable an hour after you turn off please?

All the doors and the bonnet need to have been closed for at least an hour before check that flow.
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post #12 of 18 Old 06-18-2021, 09:32 AM Thread Starter
Kiwimg
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Meter is only telling me the battery voltage, it dropped down to 9.5 while I was driving; I’m assuming because it was using power

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post #13 of 18 Old 06-18-2021, 09:39 AM Thread Starter
Kiwimg
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I guess the alternator was the culprit after all of this. After taking it apart it was found to have bad brushes. Replaced alternator, and back to working. Only thing that has happened now is that the TCM is throwing a code and the idiot lights will flash then go out and engine will stop. When I restart the engine it will run fine. Looks like I may need a new TCM now as well!

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post #14 of 18 Old 06-18-2021, 12:08 PM
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caution, this guy is full of opinions and other stuff..."Delta0" i would ignore his bs...

99wj, 150,000 miles
00xj ,189,000 miles
10hummer3,76,000 miles
98xj, 133,000 miles
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post #15 of 18 Old 06-18-2021, 12:55 PM
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Quote:
Originally Posted by 2oldjeeps View Post
caution, this guy is full of opinions and other stuff..."Delta0" i would ignore his bs...
Thank you for your feedback 2oldjeeps.
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