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Unread 07-11-2013, 01:24 PM   #1
ID10Tpig
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1999 XJ Cherokee 
 
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Location: Tomball, TX
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Jeep xj over charging with rpm

So I ran over something on the beach and then it died and I couldn't get it to start. Found a blown fuse for the auto engine shutdown and replaced it and now it starts but now I have about 13.8 volts on the gauge at idle and then it goes up with the rpm past 15, 16 and 17 volts. Nothing looks messed up, and the only thing that got hit was the alternator but no wires are damaged and nothing is physically damaged.
Oh please help.
It's a 99 with a 4.0 and an aw4

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Unread 07-11-2013, 05:21 PM   #2
CJ7-Tim
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Test the alternator output to confirm the dash gauge readings. The alternator should charge at about 13.2V to 14.3V. If you have more or less charging, you have a wiring issue, an alternator issue, or a battery issue.

The alternator and the battery can be Load Tested at the auto parts store.
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Unread 07-11-2013, 06:03 PM   #3
ID10Tpig
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I tested at the battery and it confirmed gauge reading. I'm actually driving to auto store right with only battery to save my electronics. When the little plug with 2 green wires is plugged in, the gauge shows 15 or so volts for about 10 seconds then pegs at 19. I unplug little green wire plug but keep power wire connected to alternator and it shows about 12.8 for about 20 seconds then pegs to 0 but I still drive normally. I'm going to store replace the alternator as of now and hopefully it will fix it.
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Unread 07-11-2013, 07:33 PM   #4
ID10Tpig
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Replaced alternator, still the same. Nice regular voltage at idle, then gets high with rpms. Any ideas people?
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Unread 07-12-2013, 05:57 AM   #5
CJ7-Tim
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Perform routine maintenance of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery,starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Copper wires should be copper color, not black or green. Do the same for the grounding wires from the starter to engine block, the ground wires at the coil, and the ground wires from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds.

Place your DVOM (Digital Volt Ohm Multi-Meter) on the 20 volt scale. First check battery voltage by placing your multi-meter's positive lead on the battery's positive post ( the actual post, not the clamp)and the negative lead on the negative post. You need a minimum of 12 volts to continue testing. Next, leave your meter connected and take a reading while the engine is cranking. Record this voltage reading. Now connect your positive lead to the battery terminal stud on the starter and the negative lead to the starter housing. Again, crank the engine and record the voltage reading. If the voltage reading at the starter is not within 1 volt of battery voltage then you have excessive voltage drop in the starter circuit.

Typical voltage drop maximums:

• starter circuit (including starter solenoid) = 0.60 volt
• battery post to battery terminal end = zero volts
• battery main cable (measured end to end) 0.20 volt
• starter solenoid = 0.20 volt
• battery negative post to alternator metal frame = 0.20 volt
• negative main cable to engine block = 0.20 volt
• negative battery post to starter metal frame = 0.30
• battery positive post to alternator b+stud = 0.5 volt with maximum charging load applied (all accessories turned on)
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Unread 07-12-2013, 09:49 PM   #6
ID10Tpig
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Ok so nothing else makes sense and I think I fried the voltage regulator in the PCM. I dont want an external one if I know thats the problem, I would rather have it fixed right. Also, can anyone shed some light on the green and green/ orange stripe field wires coming off the alternator? And what volatges they should have.
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Unread 07-12-2013, 10:55 PM   #7
87cherokeecheif
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It's a bad ground
image-763405060.jpg
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Unread 07-12-2013, 10:58 PM   #8
xrunndonex
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Tell you the truth id just replace all the cables in the charging system also upgrade to a bigger gauge of wire
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Unread 07-12-2013, 11:59 PM   #9
ID10Tpig
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I honestly need to know specifics on the field wires for the alternator, because what I hit actually sliced into both wires and triggered the Auto Shutdown. I replaced that fuse and i can start the jeep but no voltage control. So i think it literally shorted the wires together and zapped the regulator inside the PCM.
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Unread 07-13-2013, 08:14 AM   #10
CJ7-Tim
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PCM failure is very highly unlikely.

Damaged wires and/or dirty wire connections result in poor current flow. The PCM senses low voltage and runs the alternator wide open, and you see 15-16-17 volts on the dashboard gauge.

Use your $6-18 Volts Ohms Multi-Meter that you bought at the local hardware store, home improvement store, or WalMart type store and perform the voltage drop tests. While testing, remove and clean all the wire connections, and look for damaged wires.
__________________
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Between 2009 when Obama took office, and 2013, median annual household incomes have fallen by more than $2,100.

Progressive Liberalism: Bringing you new Healthcare ideas so wonderful, they have to include mandatory participation ......

Originally Posted by Ronald W. Reagan: Government is not the solution to our problems; Government is the problem.
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