Voltage regulator???? - JeepForum.com
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post #1 of 55 Old 01-09-2017, 12:43 PM Thread Starter
JimSmith
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Voltage regulator????

Here's what's been happening and what I've done so far.

Driving along and volt gauge drops to zero, first time this happened got to the house shut it off then immediately restarted the engine volt gauge shows a bit over 14 volts. Checked with a volt meter to battery terminals 14.2 volts, so figured it was just one of those freaky things and dismissed the idea of an issue.

A few days later and maybe 40-50 miles it does it again volt gauge drops to zero, get it home leave it running and check with volt meter 12.3 volts at battery. Shut it off turn the key on and volt gauge shows 12.3 volts, start it up and still 12.3 on gauge and volt meter. OK, I figure it's the alternator order in a new unit and begin cleaning all the terminals through out the charging system including all the grounds from the battery to the block to the body.

New alternator gets to the house hook everything up drive it for 3 days maybe another 50 miles and this afternoon the volt gauge drops to zero, get it home put the volt meter to it while it's still running and 12.2 volts at the battery. Shut the engine off and turn the key to the run position and volt gauge shows slightly above 12 volts. Restart engine and still 12 volts on the gauge, check with the volt meter 12.2 at the battery. Shut it off and restarted a few times and still 12 volts at the gauge.

Then after I don't know maybe the 5th time of restarting the engine, low and behold volt gauge jumps up to 14+ volts check with the volt meter at battery 14.4 volts.

I'm beginning to think the voltage regulator in the PCM is acting up. Does this sound familiar to any of you???? Would this be a symptom of the voltage regulator being on it's last leg, or is something else going on????. Hate to dump $200 into a PCM and find out it's not the problem. The engine is running just fine even without the alternator working, no codes, no CEL, just the "check gauges" light when the volt gauge drops to zero.


'98 Chili Pepper 2.5, AX5, 33x12.5x15, 5.13, D30 Aussie, Super 35
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post #2 of 55 Old 01-09-2017, 01:02 PM
Jerry Bransford
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Before assuming it's the voltage regulator inside the PCM, the first thing to do is to eliminate the battery connections as a possible cause of that issue.

Physically remove both battery connectors and use a wire brush or a battery wire brush set to clean both the battery posts and the inside of the connectors. Then reinstall them and make sure the battery clamps are tightened sufficiently to prevent movement even with considerable hand pressure. Bad/weak/loose/corroded/dirty battery connections very commonly cause erratic/intermittent alternator issues and voltmeter problems.

NO, just looking at the battery connections and thinking they look ok won't be good enough. This kind or problem doesn't require a battery connector problem to be visible.

If you don't own a wire brush, go buy a battery brush kit... they're only $4 or so at any auto parts store.
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post #3 of 55 Old 01-09-2017, 01:05 PM Thread Starter
JimSmith
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did that Jerry

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post #4 of 55 Old 01-09-2017, 01:26 PM
Jerry Bransford
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Quote:
Originally Posted by JimSmith View Post
did that Jerry
That would have been very good information to have already included.

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post #5 of 55 Old 01-09-2017, 01:28 PM
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So this is not an uncommon problem, I had it myself on my '98 and have read others who have had it. I've not once heard of it being an actual alternator issue.

In most cases this is a failing battery or poor/dirty connection issue. In my case it was a failing battery although I didn't realize it for quite some time because the battery would still start the engine just fine and seemed OK otherwise. I finally had the battery checked (Diehard Gold) and it failed. Replaced under warranty, haven't had the issue since and it's been long enough to know this was the fix.

Quote:
New alternator gets to the house hook everything up drive it for 3 days maybe another 50 miles and this afternoon the volt gauge drops to zero, get it home put the volt meter to it while it's still running and 12.2 volts at the battery. Shut the engine off and turn the key to the run position and volt gauge shows slightly above 12 volts. Restart engine and still 12 volts on the gauge, check with the volt meter 12.2 at the battery. Shut it off and restarted a few times and still 12 volts at the gauge.

Then after I don't know maybe the 5th time of restarting the engine, low and behold volt gauge jumps up to 14+ volts check with the volt meter at battery 14.4 volts.

I'm beginning to think the voltage regulator in the PCM is acting up.
Actually I think this is a good indicator the voltage regulator is working. After running for a while the battery is charged up, so 12.2 at the battery is normal. After you started it 5+ times (without giving time to charge) you drained the battery enough to tell the system to charge and then got your 14+ volts.

Have your battery checked. If its not that check your connections (not just at the battery but also at at the grounds and the PDC).


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post #6 of 55 Old 01-09-2017, 01:33 PM Thread Starter
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Quote:
Originally Posted by Jerry Bransford
That would have been very good information to have already included.
Quote:
Originally Posted by JimSmith View Post
Here's what's been happening and what I've done so far.
A few days later and maybe 40-50 miles it does it again volt gauge drops to zero, get it home leave it running and check with volt meter 12.3 volts at battery. Shut it off turn the key on and volt gauge shows 12.3 volts, start it up and still 12.3 on gauge and volt meter. OK, I figure it's the alternator order in a new unit and begin cleaning all the terminals through out the charging system including all the grounds from the battery to the block to the body.
Not to be a wise "A" but I thought I did LoL

'98 Chili Pepper 2.5, AX5, 33x12.5x15, 5.13, D30 Aussie, Super 35
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post #7 of 55 Old 01-09-2017, 01:37 PM
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As Jerry says, be sure you have checked all connections... including the plug connectors at the PCM & where the alternator output wire bolts to the PDC.


Not exactly a common problem for the regulator in the PCM to fail but does seem to happen. There are external regulators available to bypass the PCM. Several on these forums have used this one. Also note there is an option (FRM) that fools the PCM & keeps the CEL from coming on. At least one member has reported some voltage pulsating with that regulator but no others have reported it that I have seen. So do some research.
External Regulator Conversion Kit for Jeep.


http://alternatorparts.com/external-...nator-kit.html
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post #8 of 55 Old 01-09-2017, 01:52 PM Thread Starter
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Quote:
Originally Posted by Rubi4MyMrs View Post
As Jerry says, be sure you have checked all connections... including the plug connectors at the PCM & where the alternator output wire bolts to the PDC.


Not exactly a common problem for the regulator in the PCM to fail but does seem to happen. There are external regulators available to bypass the PCM. Several on these forums have used this one. Also note there is an option (FRM) that fools the PCM & keeps the CEL from coming on. At least one member has reported some voltage pulsating with that regulator but no others have reported it that I have seen. So do some research.
External Regulator Conversion Kit for Jeep.


http://alternatorparts.com/external-...nator-kit.html
I have looked the 3 PCM connections they don't looked corroded or dirty in anyway, need to pickup some dielectric grease to put a light coat on them though. The alternator output goes to the PDC???? Guess I need to dig a little deeper then. It looked like just by following the wire loom that it went straight to the battery.

Ya I've looked at those external kits and am thinking about doing it. Only thing I haven't found on them is if the volt gauge will still work when the PCM is taken out of the loop. That's easy enough to find out if I decide to go that way. Then again if it's just something I have overlooked that's a low cost fix why blow another $70 on that kit.

I might add not new to auto mechanics just new to this type of charging system.

EDIT: Yup found that ALT output wire on the PDC..... Was a little dirty and not exactly tight tight....Maybe that'll do it....Will let y'all know

'98 Chili Pepper 2.5, AX5, 33x12.5x15, 5.13, D30 Aussie, Super 35

Last edited by JimSmith; 01-09-2017 at 02:08 PM.
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post #9 of 55 Old 01-09-2017, 05:31 PM
festerw
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Did you get a new alternator or a reman unit? I've had a couple remans fail a couple days after install and act the way yours is.

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post #10 of 55 Old 01-09-2017, 05:37 PM Thread Starter
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Quote:
Originally Posted by festerw View Post
Did you get a new alternator or a reman unit? I've had a couple remans fail a couple days after install and act the way yours is.
New

'98 Chili Pepper 2.5, AX5, 33x12.5x15, 5.13, D30 Aussie, Super 35
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post #11 of 55 Old 01-10-2017, 01:09 AM
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Where did you buy it?...
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post #12 of 55 Old 01-10-2017, 04:17 AM Thread Starter
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post #13 of 55 Old 01-11-2017, 09:42 PM Thread Starter
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Yeah well all of the things mentioned in this thread were great ideas, unfortunately none of them were the right things. So back to square one, voltage regulator in the PCM has got to be bad. Even the battery temp sensor checks out with in specs. So just going to go ahead and do the separate external voltage regulator suggested by Rubi4MyMrs.
Thanks for the input Y'all

'98 Chili Pepper 2.5, AX5, 33x12.5x15, 5.13, D30 Aussie, Super 35
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post #14 of 55 Old 01-14-2017, 03:46 PM Thread Starter
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So got the External Voltage regulator kit from Quick Start in the mail today. Very easy install, at first I was going to tie into the Rear Defrost switched + in the PDC ( I have a soft top no need for the rear defrost), voltage at the battery was peaking at 15.5 not good. So went to an always hot terminal in the PDC and dropped down to 14.4. Started digging around looking for a good switched power source for the VR and, then thought check the IGN voltage at the PCM in the old ALT wiring harness,12.5 without it running key in run 0.1mA with the key off. Tied into it for the IGN source for the VR and perfect 14.4 volts at the battery. No voltage pulse with or without the lights on and handles all the accessories just fine. No CEL, no codes, no problems!

So I'm going to assume the PCM has an issue on the field side of the charging circuit.

https://shop.alternatorparts.com/hd-...ment-kit.html/

'98 Chili Pepper 2.5, AX5, 33x12.5x15, 5.13, D30 Aussie, Super 35
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post #15 of 55 Old 01-14-2017, 05:02 PM
Rubi4MyMrs
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Thanks for the detailed follow up report. Especially getting the proper charge rate & that it does not cause voltage pulsing.
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