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Problems with My jeep wrangler
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Toni12
New User
Apr 14, 2013, 5:02 PM
Post #1 of 2
(1500 views)
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Problems with My jeep wrangler
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I have a 1995 Jeep wrangler saharah 4.0L 6cly. Its been driving me crazy lately and feeling that I am hiting brick wall after brick wall. I recently replaced my ECU and my chenck engine light came on and half my dash board didnt light up, after a couple of months my headlights went out and my brights worked but now they both dont work. My voltage in my jeep are running high, when I drive it goes above 19 and when I turn it on its a 14 the thing is is its making my batteries spirt acid out the top. I took out my alternater to have it tested and it passed with flying colors I have talked to my buddy at work he said it sounds like a voltage regulator problem but as I do research they all say the voltage regulator is inside the alternator it self so this is where I get confused and do not know what to do next Someone please help.
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Discretesignals
Ultimate Carjunky
/ Moderator
Apr 14, 2013, 5:22 PM
Post #2 of 2
(1478 views)
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Re: Problems with My jeep wrangler
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Wow, 19 volts will definitely cause problems with ECUs.
The voltage regulator is inside the PCM.
You can tell if there is a problem with the alternator when there is an overcharge by unplugging the electrical connector on it. If the voltage goes to battery voltage, the alternator isn't the problem unless the field on the ground side is shorted inside the alternator (rare). You can tell if that is the case by ohm checking the field circuit in the alternator to see if it has continuity to the alternator's case.
If the alternator isn't the problem, that leaves two things. The field ground control is shorted to ground or the voltage regulator in the PCM is faulty and full fielding the alternator.
There is a dark green wire on the alternator connector that runs from the alternator to the PCM. That is the field's ground. The field is ground controlled by a driver in the PCM. This is how the PCM regulates the output of the alternator.
Check that wire for shorts to ground. If the wire isn't shorted to ground, the PCM is the culprit.
Checking for a short to ground on that wire is fairly simple.
(1) disconnect the battery negative terminal
(1) unplug the alternator connector
(2) unplug the PCM connector(s)
(3) take an ohm meter and connect one lead to the battery negative terminal that you disconnected in step 1. Take the other lead and probe the dark green wire terminal in the alternator connector.
(4) If you show continuity to ground, the wire is shorted somewhere.
If you have a 12 volt test lamp, you can use that too.
(1) With battery negative disconnected unplug the PCM connector(s) and alternator connector
(2)Reconnect the battery negative terminal
(3) Connect your test lamp clamp to battery positive and probe the dark green terminal in the alternator connector.
(4)If the lamp illuminates, the circuit is shorted to ground.
**It is good practice to always disconnect the battery when connecting and disconnecting PCM connectors.**
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Apr 14, 2013, 5:49 PM)
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