Thread: Replacement Voltage Regulator

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  1. #1 Replacement Voltage Regulator 
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    Long story short I've been having intermittent issues with the voltage regulator on my jeep for the last few years, recently it's gotten to the point where I have replaced it 2 times in the last year using junk yard regulators that I cut off harnesses as the voltage regulator located behind the alternator is a dealer only part and I was quoted $255 for that little black box. As it is I ended up having to cancel a wheeling trip this last weekend as it went out and kind of left me high and dry, but works intermittently if I tap it lightly so I'm pretty much done with it at this point. When I installed the last 2 I replaced I soldered the 2 wires that needed to be spliced and made sure they were wrapped up good to prevent a short and have the voltage regulator grounded to the engine block just like the original was but these things keep going out and I can't figure out why. I don't believe I have a short anywhere as I had another unrelated electrical issue a few months back and I ended up having to unravel and re-wrap about 90 percent of the engine and tranny harnesses to find the short. My question is kind of two fold, first what could be causing these to go bad so often and secondly is there another alternative that you guys have used successfully, like an external voltage regulator from like a Ford, Dodge or Chevy that you could easily find at like an AutoZone or some local parts place.

    Thanks,
    Fred R.
    97 ZJ, 5" Long Arm Lift, Currie Anti-Rock, Beadlocked 35's, 231/D300 Doubler, Locked Front & Rear (Narrowed HP D44 w/ chromo shafts and Yukon Superjoints & F8.8), ARB Bull Bar & 9K winch, 1-Ton Hydro-assist steering, "Custom" body work and some other goodies...
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  2. #2 Re: Replacement Voltage Regulator 
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    The regulator is in the pcm. I thought that box was the field switch.
    97 grand cherokee ltd, 5.2, white, many mods of debatable value.
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  3. #3 Re: Replacement Voltage Regulator 
    ....... Lifetime Supporter rstrucks's Avatar
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    I would try a different PCM if you have access to one.

    This link may help you if you want to do the external regulator - http://www.thedieselgarage.com/forum...ad.php?t=58251
    Last edited by rstrucks; 07-21-2010 at 09:53 AM.
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  4. #4 Re: Replacement Voltage Regulator 
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    from the fsm.

    VOLTAGE REGULATOR
    The Electronic Voltage Regulator (EVR) is not a
    separate component. It is actually a voltage regulating
    circuit located within the Powertrain Control
    Module (PCM). The EVR is not serviced separately. If
    replacement is necessary, the PCM must be replaced.
    Operation: The amount of DC current produced
    by the generator is controlled by EVR circuitry contained
    within the PCM. This circuitry is connected in
    series with the generators second rotor field terminal
    and its ground.
    Voltage is regulated by cycling the ground path to
    control the strength of the rotor magnetic field. The
    EVR circuitry monitors system line voltage and battery
    temperature (refer to Battery Temperature Sensor
    for more information). It then compensates and
    regulates generator current output accordingly. Also
    see Charging System Operation for additional information.
    that box on the alternator is only the field terminal unit.
    Last edited by ratmonkey; 07-21-2010 at 11:11 AM.
    97 grand cherokee ltd, 5.2, white, many mods of debatable value.
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  5. #5 Re: Replacement Voltage Regulator 
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    Quote Originally Posted by ratmonkey View Post
    from the fsm.

    that box on the alternator is only the field terminal unit.
    Thanks ratmonkey, saw your post last night but couldn't post from my phone (just moved and no internet access at the new place yet), after seeing it I ended up taking apart that "box" that's posted behind the alternator and all it was was just the 2 wires and the ground cable going into it and the cables were just boxed in with that plastic essentially, nothing else. Cleaned up the wiring and replaced the connectors but it still doesn't work, which is funny because replacing this "box" fixed the problem the last couple of times. Funny thing is I still have the problem but if I tap the alternator in the same area the black "box" used to be bolted behind it the system will start charging again . I had the alternator and the battery tested yesterday and they both tested good, but I think it might be the alternator so I'm going to get one today after work. I also took the entire harness in that area apart inspected and cleaned it and the alternator & battery/terminals.

    rstrucks, I don't have access to a PCM so I would have to get one from a JY and hope it works. The first time this happened I got a quote from the dealership for $475 for the PCM or $200 to diagnose it but it would have to be sent off and would take 4-5 days as they said they could not see if it was bad with just the basic scan tool. Correct me if I'm wrong but I believe that the PCM has to be from the same Year and engine combo as mine so as to work? Thanks again for the help, I'll update the post with the resolution if/when I find it.

    Thanks,
    Fred R.
    97 ZJ, 5" Long Arm Lift, Currie Anti-Rock, Beadlocked 35's, 231/D300 Doubler, Locked Front & Rear (Narrowed HP D44 w/ chromo shafts and Yukon Superjoints & F8.8), ARB Bull Bar & 9K winch, 1-Ton Hydro-assist steering, "Custom" body work and some other goodies...
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  6. #6 Re: Replacement Voltage Regulator 
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    Quote Originally Posted by fredr1980 View Post
    Cleaned up the wiring and replaced the connectors but it still doesn't work, which is funny because replacing this "box" fixed the problem the last couple of times.
    My best guess as to why it happened is that there is an intermittent electrical problem (probably a loose wire causing a short or some sort of faulty logic in the PCM) somewhere else is causing that box operate out of its intended electrical specs and eventually fail. Because it's intermittent, that would explain why replacing the box worked -- until it died again.

    If that box's inputs are fed by the PCM, I'd put my money on the PCM. I've had really really weird intermittent electrical issues for a while until I replaced the PCM and they all magically went away.
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  7. #7 Re: Replacement Voltage Regulator 
    Senior Member jborushko's Avatar
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    Quote Originally Posted by fredr1980 View Post
    ... I don't have access to a PCM ...
    what motor do you have? i have a pcm from a 96 4.0 larado from my old motor
    96 ZJ swapped in 5.2, 242, 14bolt rear, big ugly home brew bumper, 7.5" of lift in the front 9" in the rear, long arms, hummer wheels with 37s... (dont worry front axle is next)

    It should be heavy. Weight is a sign of reliability. If it doesn't work, you can always hit him with it.

    -e-boner
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  8. #8 Re: Replacement Voltage Regulator 
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    Quote Originally Posted by rstrucks View Post
    I would try a different PCM if you have access to one.

    This link may help you if you want to do the external regulator - http://www.thedieselgarage.com/forum...ad.php?t=58251
    Thanks that helped as it fixed the issue last night, I ended up using the a write-up on another Cherokee forum were they used the same Pre-89 dodge external voltage regulator but said to splice it into the green wire w/ purple tracer on the alternator with the blue wire on the regulator and the solid dark green wire on the alternator gets cut and sent to the light green wire on the plug for the regulator.

    Quote Originally Posted by jborushko View Post
    what motor do you have? i have a pcm from a 96 4.0 larado from my old motor
    PM sent... Might need one as a back-up

    Thanks again to everyone for all the help again.

    Fred R.
    97 ZJ, 5" Long Arm Lift, Currie Anti-Rock, Beadlocked 35's, 231/D300 Doubler, Locked Front & Rear (Narrowed HP D44 w/ chromo shafts and Yukon Superjoints & F8.8), ARB Bull Bar & 9K winch, 1-Ton Hydro-assist steering, "Custom" body work and some other goodies...
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  9. #9 Re: Replacement Voltage Regulator 
    Senior Member jborushko's Avatar
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    Quote Originally Posted by fredr1980 View Post
    ...I ended up using the a write-up on another Cherokee forum...
    link?
    96 ZJ swapped in 5.2, 242, 14bolt rear, big ugly home brew bumper, 7.5" of lift in the front 9" in the rear, long arms, hummer wheels with 37s... (dont worry front axle is next)

    It should be heavy. Weight is a sign of reliability. If it doesn't work, you can always hit him with it.

    -e-boner
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  10. #10 Re: Replacement Voltage Regulator 
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    Quote Originally Posted by jborushko View Post
    link?
    LINK

    Got your PM...

    Fred R.
    97 ZJ, 5" Long Arm Lift, Currie Anti-Rock, Beadlocked 35's, 231/D300 Doubler, Locked Front & Rear (Narrowed HP D44 w/ chromo shafts and Yukon Superjoints & F8.8), ARB Bull Bar & 9K winch, 1-Ton Hydro-assist steering, "Custom" body work and some other goodies...
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