Voltage regulator - JeepForum.com
 
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post #1 of 12 Old 07-14-2011, 07:12 PM Thread Starter
19YJ91
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Voltage regulator

Ok so I have had the jeep die on me 2 times now and both times the battery was dead put a charged one in and it started right up. I went to autozone had them run their charing test on it and it said faulty voltage regulator. The guy prices me a new altenator. However I pulled out the trusty haynes manual and it said the voltage regulator is in the pcm. So does this mean I need a new pcm or is there anything else should try first? Jeep is a 97 5.2 limited.

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post #2 of 12 Old 07-14-2011, 07:14 PM Thread Starter
19YJ91
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Also I was driving with radio on once and the second time I had radio, wipers, and headlights on. I have drove it a few times since not as far with out these things on and had no issues with it dying.
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post #3 of 12 Old 07-14-2011, 08:36 PM
JS97ZJ
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If you turn on the headlights and blower with the engine running at 1000 rpms, what does the voltage gage indicate?

When the PCM see a drain on the battery, it turns on the generator though the 2 small terminals on the back. Also check the belt tension.
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post #4 of 12 Old 07-15-2011, 09:35 AM Thread Starter
19YJ91
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I will check when I get home tonight and post.
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post #5 of 12 Old 07-16-2011, 09:23 PM Thread Starter
19YJ91
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the voltage gauge never changed. it was sitting a little under 14 v. 13v range
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post #6 of 12 Old 07-17-2011, 06:45 AM
JS97ZJ
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Then your battery is getting charged.

Check the battery water level, belt tension, connections plus the grounds.
You can check the acid health with a cheap hydrometer $3-4 bucks.


Is the battery over three years old? Some will fail even before the warranty is up. I had to replace mine in January. It went bad just under the warranty. I had it replaced with a new 900 cca for free. You should have a cca rating of 650 or more with the 5.9. The bigger the better.

Many guys recently have been having problems with their Jeeps dying over night due to a drain being caused by the rear hatch ajar switch getting shorted out. This causes the BCM not falling to sleep after the courtesy time out shuts down. The drain is like 180 ma.
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post #7 of 12 Old 07-17-2011, 07:17 AM Thread Starter
19YJ91
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it never dies sitting I was driving it both times. It died and the only way to get it started was to put in a charged battery. The little tester at autozone said the voltage regulator was faulty but I didn't know if there was something else that might cause it to give that reading or if I needed to replace the pcm.
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post #8 of 12 Old 07-17-2011, 08:08 AM
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There are other things that could prevent the regulator from not responding so instead of typing out all of it (I'm a 2 finger typist) here it comes.....
Check the tray sensor.......
Attached Thumbnails
bat1.PNG   bat2.PNG   bat3.PNG   bat4.PNG   bat5.jpg  

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post #9 of 12 Old 07-17-2011, 08:09 AM
JS97ZJ
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and more.............
Attached Thumbnails
bat6.PNG  
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post #10 of 12 Old 07-18-2011, 08:11 AM
MaintMech
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Thanks JS97ZJ!

Very useful.

'96 Grand Laredo, 4.0, Stock, Daily Driver

I fought Oracle and Oracle won!

Originally Posted by coralman
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post #11 of 12 Old 07-19-2011, 12:51 AM
squazz
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So do certen years have an internal, and other years have an external Voltage Regulator or will a 98 5.9 work on a 93 4.0 ?
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post #12 of 12 Old 07-19-2011, 07:06 AM
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Quote:
Originally Posted by squazz View Post
So do certen years have an internal, and other years have an external Voltage Regulator or will a 98 5.9 work on a 93 4.0 ?
If you research historical Jeeps you'll find the regulators were separate modules. All older vehicles were.

With the advent of the computerized electrical systems, it became cheaper and regulators became a more functional part of the overall monitoring of the electronics.

The ZJ"s all have regulators in the PCMs. The 93 has a totally different computer design and won't work with the 96-98 models. There are aftermarket kits that are available to jump out the defective regulator portion of the PCM, but you'll still have the CEL constantly on dash......so you'll never know if a new problem has arisen.

I had a problem with my regulator a few years back that that gave me intermittent charging symptoms and with the troubleshooting guide ^^^, found out the block attached to the back of the generator that contained the 2 field connection leads had a cold solder joint preventing the PCM from controlling the generator's on and off function.
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