1999 WJ Overcharge? Run poorly questions - JeepForum.com
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post #1 of 19 Old 03-17-2010, 06:43 PM Thread Starter
spgeid
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1999 WJ Overcharge? Run poorly questions

So I bought this WJ. Maybe a big mistake. But...

With the alternator unplugged it runs not too bad. If I plug it in the engine dies down to nearly a stall. Checked the voltage at the battery it is charging at 16 to 17 volts.

Is this enough load to draw the engine to a stall? Or is there another underlying problem? Could the coil pack be overdrawing?

I just change the twin california cataylitics because they back was was plugged. I think it was really red hot from the looks of it.

Anyone have any suggestions besides sell quick?

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post #2 of 19 Old 04-24-2010, 02:40 PM
TK32
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Same problem

To bad no one has replied yet mine does the same thing and the gauges start acting up! If you have solved problem please post what you found,thanks tk32

Last edited by TK32; 04-24-2010 at 02:42 PM. Reason: more info
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post #3 of 19 Old 04-24-2010, 03:49 PM
euphoria
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check the battery terminals, wj's do very crazy things when the terminals have any corrosion of any kind on them
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post #4 of 19 Old 04-24-2010, 08:51 PM
TJSWJ
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The voltage regulator in the alternator is most likely bad. The jeep is designed to run at 14.6v when charging. If its charging 16+ volts then its throwing the computer and all the sensors off
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post #5 of 19 Old 04-25-2010, 07:54 AM
TK32
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Changed voltage regulator still over charged,replaced alternator still same thing. when voltage regulator wire is unplugged vehicles runs almost perfect, plug it back in and it starts to buck skip it's strange. Battery terminals are nice and clean tk32
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post #6 of 19 Old 04-25-2010, 08:11 PM Thread Starter
spgeid
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Here is what I learned.

The charging system on the 99 WJ is completely controlled by the PCM. If you have an overcharge the PCM needs replaced. My gauge was acting goofy on the dash also. Change out the PCM and fix the bucking engine problem, gauge problem and charges at the right voltage now. I found the best buy on E-bay from a PCM exchange company in Florida. $150 shipping included. They were reasonably fast also. About 4 days to get mine. The alternator itself on the 99 WJ (mine was a bosch) does not have any regulator built into the unit.
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post #7 of 19 Old 05-02-2010, 11:16 AM
TK32
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Where is pcm located on this vehicle?
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post #8 of 19 Old 05-02-2010, 12:55 PM Thread Starter
spgeid
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PCM location

On the firewall on the passenger's side.
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post #9 of 19 Old 05-04-2010, 09:24 AM
TK32
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thank you I'm going to replace it. When I got this Jeep I was told voltage regulator and then alternator were replaced thank's for the info about how this charging system works, they should have left the charging duties out of the computer it would have made things easier! thanks again tk32
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post #10 of 19 Old 06-15-2013, 09:47 PM
Chevymanjohniii
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I'm having the same problem with a 99 WJ I just bought for my wife. It toasted the battery an a hurry but then again that's what I'd expect. I came to the conclusion that the ECU was the overcharging culprit, but I wasn't sure if it would cause the volt gauge to not work. It drops when the key is off and comes up a little when the key is on but that's it. Will replacing the ECU fix that too does anyone know? I haven't been able to find a good pin out diagram for the ECU so I can check out some wires. Thanks in advance for any help.
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post #11 of 19 Old 05-15-2015, 11:08 AM
AdamBucy
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I have a similar issue with mine. It puts 19v to the battery when it's running then the gages go a screwy. I tried my pcm in my buddy's jeep (same year as mine 99) and it worked fine and only put 14v to his battery. I have a new alternater as well.
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post #12 of 19 Old 05-16-2015, 07:01 AM
Darnice
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You say the Battery terminals are nice and clean. Maybe. They look clean but you need to check.
Start it and:
Get your volt meter out and measure the voltage on the battery posts, not the connectors, the post themselves. Then measure the voltage on the battery connectors, they have to be the same.
I have seen many "My terminals are clean" only to find they are but are not making good contact to the battery posts. The inside of the connectors can literally corrode inside out and "look" perfectly fine.
Don't throw any money at it until you verify the voltage at the battery posts.
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post #13 of 19 Old 05-17-2015, 08:33 AM
AdamBucy
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Thanks for the tip. I will check this today and repost results. I've eliminated the battery temperature sensor and tries my pcm in another 99 and it regulates the volts just fine. So I'm back to either alternator or battery. It's just weird because it makes my gages go all screwy.
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post #14 of 19 Old 05-17-2015, 11:19 AM
86cj74.2L
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Quote:
Originally Posted by AdamBucy
Thanks for the tip. I will check this today and repost results. I've eliminated the battery temperature sensor and tries my pcm in another 99 and it regulates the volts just fine. So I'm back to either alternator or battery. It's just weird because it makes my gages go all screwy.
it may also be the wiring between the PCM and battery. Where it's not able to sense the system voltage correctly. You have no codes for the charging system, correct?
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post #15 of 19 Old 05-18-2015, 08:37 AM
AdamBucy
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correct. I don't even get a check engine code. I start it up and it fires up fine. Then very shortly the voltage meter on the dash goes to 19 (which was confirmed with my multi meter) Then the gages all go crazy, and the battery starts to boil.
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