97 TJ Voltage Regulator Failure - JeepForum.com
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post #1 of 20 Old 11-04-2016, 12:38 PM Thread Starter
SmashinTJs
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97 TJ Voltage Regulator Failure

Good afternoon everyone,

I have been having some electrical issues with the Jeep and I am having a tough time deciphering what I need to fix/replace.

The issue: While driving Voltmeter will occasionally drop to 9 (or lower). The problem first occurred a couple months back and didn't repeat again until this week. The Jeep will continue to run normally (no rough operation, even at idle) with the voltmeter in the tank. Once it drops it will stay pegged at the bottom until the Jeep is shut off and is turned back on. Once I shut the Jeep down it will fire right up with no delayed starting/cranking. Once it restarts the voltmeter will display 14 volts again and will remain at 14 volts while driving for anywhere from 30 seconds to 20 mins. There is no regularity to it falling again.


It recently threw a code 47: low battery voltage and/or low alternator output

I took the Jeep down to autozone and they tested the electrical system and the battery (Optima Yellow Top) tested ok. Their machine says the voltage regulator failed.

I have been reading up on this and I cannot seem to get a straight answer on whether the voltage regulator is in the alternator on the 1997 TJ or whether it is in the PCM.

I need to know what I need to replace and I dont have the $$ to just start replacing every single thing that "could" be wrong.

and just the get it out of the way now, yes, I have cleaned the battery connections/terminals and ensured they are FIRMLY connected to the battery posts.

Again 1997 TJ 4.0L 170K miles.


Any help would be much appreciated guys!

Cheers!

Steve


RED 1997 Modded TJ l 3.5 Rancho l PIAA's l 33'' KM2 l Custom Yakima Roof Setup l Armor l.

TJ TECH BOOT CAMP: READ IF NEW


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Is that bumper weighted to keep you from catching air at highway speed?
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Well no (why would it) :confused:
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post #2 of 20 Old 11-04-2016, 12:52 PM
Jerry Bransford
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All TJ voltage regulators are located inside the PCM.

When you have a choice, buy American made.
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post #3 of 20 Old 11-04-2016, 12:54 PM Thread Starter
SmashinTJs
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Quote:
Originally Posted by Jerry Bransford View Post
The TJ's voltage regulator is inside the PCM, it is definitely not in the alternator or in an external location.
Thanks for clearing that up Jerry.

Now would Autozone's test result of a failure of the voltage regulator be diagnostic enough to pull the trigger on a new PCM?

Any other testing I can perform to rule out a bad alternator? (The cheaper fix)

Thanks!

RED 1997 Modded TJ l 3.5 Rancho l PIAA's l 33'' KM2 l Custom Yakima Roof Setup l Armor l.

TJ TECH BOOT CAMP: READ IF NEW


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Quote:
Originally Posted by scavanau View Post
Is that bumper weighted to keep you from catching air at highway speed?
Quote:
Originally Posted by NorthWhiteWolf View Post
Well no (why would it) :confused:
Quote:
Originally Posted by scavanau View Post
Because I think your fender flares could easily pass for wings
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post #4 of 20 Old 11-04-2016, 12:57 PM
Jerry Bransford
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I dunno how Autozone could definitively say the voltage regulator inside the PCM has failed when all they tested was the alternator. Well I guess I do know how... they're clueless about most things and cluelessly assumed the VR is inside the alternator as is common on other vehicles.

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post #5 of 20 Old 11-04-2016, 01:01 PM
Rubi4MyMrs
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The voltage regulator is in fact integrated into the PCM. You can save getting another PCM by going to an external regulator. There is one that has an added benefit of turning off the CEL (called FRM) which may be a problem with some so check that. Some users have reported getting some pulsing in light brightness so do some research.

External Regulator Conversion Kit for Jeep.

http://alternatorparts.com/external-...nator-kit.html

Also:


https://www.jeepforum.com/forum/f9/ba...41/index2.html


Pulsing Lights:

https://www.jeepforum.com/forum/f9/pu...ights-1528045/
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post #6 of 20 Old 11-04-2016, 04:34 PM
freeskier93
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The auto part store test absolutely should not be trusted for voltage regulator failure. It can barely be trusted for battery testing.

It's probably the battery, how old is the yellow top?
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post #7 of 20 Old 11-04-2016, 04:46 PM
CJ7-Tim
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If a TJ Wrangler or XJ Cherokee shows 9 volts on the dashboard gauge, it is almost a 99.8% probability to be an alternator issue. Usually, the brushes are worn out, or close to worn out and are sticky. If the 9 volts indication comes and goes, the sticky worn out brushes are at fault.

If the gauge shows 19 volts there is a battery issue, and/or alternator connectivity issues, something loose and/or corroded.

.

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post #8 of 20 Old 11-04-2016, 05:22 PM Thread Starter
SmashinTJs
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Yes the problem "Comes and goes". unfortunately its being coming more frequently. I swapped batteries and continue to have the same problem so I know my yellow top isnt the culprit. I guess ill take a swing at replacing the alternator and see what happens. Dealership quoted me almost 900 in parts and labor to fix the PCM so im going to be avoiding that at all costs (literally).

Thanks for the help guys
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post #9 of 20 Old 11-04-2016, 05:23 PM
Jerry Bransford
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Used/remanufactured PCMs are available on sites like eBay.

When you have a choice, buy American made.
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post #10 of 20 Old 11-04-2016, 05:26 PM Thread Starter
SmashinTJs
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Quote:
Originally Posted by Jerry Bransford View Post
Used/remanufactured PCMs are available on sites like eBay.
Ill try that next if the alternator doesnt fix it.

Thanks Jerry.

Any recommendation on alternator? Either going to get O'riley's or napa. Ive heard of ppl doing a durango 160 amp alternator but given the fact that my jeep is my DD and i cant afford to keep tinkering with problems at the moment I just want something that is going to fix the problem (hopefully)

RED 1997 Modded TJ l 3.5 Rancho l PIAA's l 33'' KM2 l Custom Yakima Roof Setup l Armor l.

TJ TECH BOOT CAMP: READ IF NEW


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Quote:
Originally Posted by scavanau View Post
Is that bumper weighted to keep you from catching air at highway speed?
Quote:
Originally Posted by NorthWhiteWolf View Post
Well no (why would it) :confused:
Quote:
Originally Posted by scavanau View Post
Because I think your fender flares could easily pass for wings
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post #11 of 20 Old 11-04-2016, 05:29 PM
Jerry Bransford
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Quote:
Originally Posted by SmashinTJs View Post
Ill try that next if the alternator doesnt fix it.

Thanks Jerry.

Any recommendation on alternator? Either going to get O'riley's or napa. Ive heard of ppl doing a durango 160 amp alternator but given the fact that my jeep is my DD and i cant afford to keep tinkering with problems at the moment I just want something that is going to fix the problem (hopefully)
Avoid store brands like from AutoZone, their quality is highly variable (often crappy) and a standard 117 amp alternator is fine. I'd probably go NAPA over O'Rileys. Or see if you can find an AC-Delco on www.rockauto.com. Rarely would the full 160 amps of the Durango be needed. My winch gets used a lot and I'm still using the same OE 117 alternator. And I've never drained the battery, not even while winching shorter pulls when I couldn't start the engine.

When you have a choice, buy American made.
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post #12 of 20 Old 11-04-2016, 06:35 PM
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Avoid any "Lifetime Warranty" Chinese refurbished units, they have a high rate of being DOA and often have a short service life. I would find a local automotive electronics shop and have an American properly rebuild the alternator using quality parts, or buy the required parts and do the work yourself. There is nothing technical involved.

.

A recent Gallup public opinion poll shows the NRA, at 58% approval, has a higher approval rating than either Hillary Clinton or Barack Obama.

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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post #13 of 20 Old 11-04-2016, 08:05 PM
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See if you can find a local DC motor repair shop and have it rebuilt?...
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post #14 of 20 Old 11-04-2016, 09:55 PM Thread Starter
SmashinTJs
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Alright so.... I replaced the alternator and.... the problem still exists. *Sigh* So i guess the voltage regulator and the PCU is the problem and now ive spent 250 ish dollars finding that out for sure.

Guess ill be on the hunt for a PCU or doing the external voltage regulator mod.

Thanks again for the help everyone.

RED 1997 Modded TJ l 3.5 Rancho l PIAA's l 33'' KM2 l Custom Yakima Roof Setup l Armor l.

TJ TECH BOOT CAMP: READ IF NEW


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Quote:
Originally Posted by scavanau View Post
Is that bumper weighted to keep you from catching air at highway speed?
Quote:
Originally Posted by NorthWhiteWolf View Post
Well no (why would it) :confused:
Quote:
Originally Posted by scavanau View Post
Because I think your fender flares could easily pass for wings
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post #15 of 20 Old 11-06-2016, 06:29 PM
MrAndersonJeep
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Garage
Let me know if changing the PCU fixes this issue. My Jeep just started doing the same thing to me. I figured it was the alternator but if you replaced that and it still is the same, I'm wondering if mine is the same.
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