Black box on top of alternator - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > ZJ Grand Cherokee Forum > Black box on top of alternator

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineRubicon Express Suspensions from CCOR 706-207-4140Smittybilt Hard Tops @ Oconee Off-Road! 706-534-9955

Reply
Unread 06-13-2013, 02:28 PM   #1
leftfield6
Where are my damn keys?
 
leftfield6's Avatar
1964  
 
Join Date: Oct 2005
Location: Beautiful South
Posts: 256
Black box on top of alternator

So, my new-to-me 5.9 has been doing a weird charging/no-charging thing. I had some posts on it in my general questions thread here --> http://www.jeepforum.com/forum/f13/n...tions-1533877/, but I want to pull this one item out into a separate thread.

Here was how I described the issue in the other thread:
Charging system - after a few days of working fine, my charging systen seems to have fritzed out on me. Driving along today, all good, suddenly my volt gauge goes to ZERO, and "check battery" begins flashing on the VIC. Still running fine, as are all the electrical items like lights, e-fan, etc. I make it back home, about 10 miles, with no drama. Now, in the driveway, it will start up, gauge reads about 10 volts or so for a minute +/-, and then it drops to zero, and check battery message. I cleaned terminals, and checked cables, they look okay.
And, after some suggestions, I updated with ths:
So, today I went down to the local FLAPS and had them do the battery test. Battery tested fine. So, since it's so damn easy to do, I pulled the alternator right there in the parking lot and took it inside so they could mount in in their testing rig. Good news/bad news is that it tested perfect. Good news, because, hey, I don't need an alternator. Bad news, cause that means I move on to the next likely fail point. I guess it's the PCM now, right?
Later, I discovered I had new symptoms, here:
If I start the Jeep and the volt gauge jumps up to about 14, it will be fine until I turn the ignition off, no matter if I drive 1 mile or 10 miles. If I start the Jeep, and the volt meter goes up to just a hair over 12, in less than half a mile, the volt gauge drops suddenly to zero concurrent with warning chimes and "Check Battery" on the VIC. Jeep will keep running, at least for a while. I really haven't pushed this too far. New thing to add here is that I plugged a cigarette lighter volt meter in, and watched it as the Jeep malfunctioned. In the case where it starts off barely above 12V, when the chimes/alarms/VIC go off, the voltage actually sometimes jumps to 13.7 or 13.8 volts. Most of the time, it doesn't, it just hovers around 12V.

Okay, so now I have new info. I feel like a detective circling his prey. Today I'm working on the Jeep, and I remembered my Dad would sometimes tap on electrical components and sometimes it would work. So, opened up the hood, positioned a voltmeter plugged into the cigarette lighter where I could see it from under the hood (it's attached to a 4 foot cord) and started using a short piece of rebar to tap on things. Not too hard, just a tap. So, engine running, voltmeter reads 12.1V
  • Tapped on PCM connectors. no change
  • Tapped on battery terminals, no change
  • Tapped on black plastic box on top wire of alternator, BINGO

Whn I tapped on that black box, the voltage meter immediately jumped up to 13.7, AND the sound of the alternator immediately changed. It went from making no discernible noise to a slight whine or whirring sound.

So, what is this magic little box?

Does it need replacing, or does my alternator need replacing?

Because the alternator had tested good, I tended to think the problem was something else, but now I'm not so sure.

__________________
(Current) 98 Grand Cherokee Limited 5.9
http://www.fuelly.com/driver/leftfield6/grand-cherokee

(former) 98 Grand Cherokee Laredo
77 CJ-5
75 CJ-5
leftfield6 is offline   Reply With Quote
Unread 06-13-2013, 03:02 PM   #2
HighLonesome
Belief In All Things Jeep
 
HighLonesome's Avatar
1995 ZJ 
 
Join Date: Feb 2005
Location: New Mexico
Posts: 5,563
No one knows what's inside the black box. Never heard of one failing either.

When you tap it, you are also tapping the alternator field coil connections. If you overtorque the small nuts it will harm the alternator. Checking the alternator on a machine isn't a foolproof test. It might not catch an intermittent problem.
HighLonesome is offline   Reply With Quote
Unread 06-13-2013, 04:29 PM   #3
leftfield6
Where are my damn keys?
 
leftfield6's Avatar
1964  
 
Join Date: Oct 2005
Location: Beautiful South
Posts: 256
Quote:
Originally Posted by HighLonesome View Post
No one knows what's inside the black box. Never heard of one failing either.

When you tap it, you are also tapping the alternator field coil connections. If you overtorque the small nuts it will harm the alternator. Checking the alternator on a machine isn't a foolproof test. It might not catch an intermittent problem.
I love the idea that no one knows what is inside the black box. Maybe it's where Chrysler put the extra HP?

Yeah, kinda figured that it was actually the alternator that was benefiting from the taps. Now I know when i start it, if it doesn't immediately jump up to 13.7V or better, just a little love tap gets the juice flowing. Once the alternator fires up, it doesn't drop back down until I turn the engine off. Then, on restart, it's a roll of the dice.

Guess I'll be getting a new alt.
__________________
(Current) 98 Grand Cherokee Limited 5.9
http://www.fuelly.com/driver/leftfield6/grand-cherokee

(former) 98 Grand Cherokee Laredo
77 CJ-5
75 CJ-5
leftfield6 is offline   Reply With Quote
Unread 06-13-2013, 05:09 PM   #4
ZeeJay1997
Registered User
1997 ZJ 
 
Join Date: Dec 2008
Location: Sweet Home, Alabama
Posts: 6,446
The black box is a terminal block for the cables and the field terminals. Take it all apart and check for loosiness and crud.
ZeeJay1997 is offline   Reply With Quote
Unread 06-13-2013, 05:26 PM   #5
LeeZJ
Registered User
1996 ZJ 
 
Join Date: Oct 2011
Location: London, England
Posts: 86
I removed that little black box that connects between 2 field coil connections. Had no effect on my charging system.

Lee
LeeZJ is offline   Reply With Quote
Unread 06-13-2013, 07:15 PM   #6
5-90
Registered User
1988 XJ Cherokee 
 
Join Date: Sep 2006
Location: San Jose, CA, Hammerspace
Posts: 5,344
Quote:
Originally Posted by leftfield6 View Post
So, my new-to-me 5.9 has been doing a weird charging/no-charging thing. I had some posts on it in my general questions thread here --> http://www.jeepforum.com/forum/f13/n...tions-1533877/, but I want to pull this one item out into a separate thread.

Here was how I described the issue in the other thread:
Charging system - after a few days of working fine, my charging systen seems to have fritzed out on me. Driving along today, all good, suddenly my volt gauge goes to ZERO, and "check battery" begins flashing on the VIC. Still running fine, as are all the electrical items like lights, e-fan, etc. I make it back home, about 10 miles, with no drama. Now, in the driveway, it will start up, gauge reads about 10 volts or so for a minute +/-, and then it drops to zero, and check battery message. I cleaned terminals, and checked cables, they look okay.
And, after some suggestions, I updated with ths:
So, today I went down to the local FLAPS and had them do the battery test. Battery tested fine. So, since it's so damn easy to do, I pulled the alternator right there in the parking lot and took it inside so they could mount in in their testing rig. Good news/bad news is that it tested perfect. Good news, because, hey, I don't need an alternator. Bad news, cause that means I move on to the next likely fail point. I guess it's the PCM now, right?
Later, I discovered I had new symptoms, here:
If I start the Jeep and the volt gauge jumps up to about 14, it will be fine until I turn the ignition off, no matter if I drive 1 mile or 10 miles. If I start the Jeep, and the volt meter goes up to just a hair over 12, in less than half a mile, the volt gauge drops suddenly to zero concurrent with warning chimes and "Check Battery" on the VIC. Jeep will keep running, at least for a while. I really haven't pushed this too far. New thing to add here is that I plugged a cigarette lighter volt meter in, and watched it as the Jeep malfunctioned. In the case where it starts off barely above 12V, when the chimes/alarms/VIC go off, the voltage actually sometimes jumps to 13.7 or 13.8 volts. Most of the time, it doesn't, it just hovers around 12V.

Okay, so now I have new info. I feel like a detective circling his prey. Today I'm working on the Jeep, and I remembered my Dad would sometimes tap on electrical components and sometimes it would work. So, opened up the hood, positioned a voltmeter plugged into the cigarette lighter where I could see it from under the hood (it's attached to a 4 foot cord) and started using a short piece of rebar to tap on things. Not too hard, just a tap. So, engine running, voltmeter reads 12.1V
  • Tapped on PCM connectors. no change
  • Tapped on battery terminals, no change
  • Tapped on black plastic box on top wire of alternator, BINGO

Whn I tapped on that black box, the voltage meter immediately jumped up to 13.7, AND the sound of the alternator immediately changed. It went from making no discernible noise to a slight whine or whirring sound.

So, what is this magic little box?

Does it need replacing, or does my alternator need replacing?

Because the alternator had tested good, I tended to think the problem was something else, but now I'm not so sure.
If you're talking about the moulded rubber box with all the pigtails coming out of it (three or four) on the back of the alternator - there are NO electronics in it. It is a "convenience block," used to keep the assorted wring on the back located properly when disconnected.

However, if you tap it and things pick back up, here are the likely causes of your trouble:
- Field coil stud nuts loose. Retorque (gently! Finger tight plus 1/4-1/3 turn is enough! You may replaces these with Nylon collar locknuts - they should be M4-0.6 or M5-0.8.)
- B+ stud nut loose. This should be M6-1.0 and can & should be replaced with a Nylon collar locknut as well.
- Field coil and/or B+ stud connections dirty - disassemble, clean, reterminate PRN.
- Corrosion/Contamination of wiring inside block. Trace out individual leads and reterminate, sealing connections.

As I said, there are NO electronics in that block to worry about - so if you can fix it through "percussion maintenance" then those are the likely causes.

Good luck! YMMV. TANSTAAFL. Void where Prohibited. Open Somewhere Else.
__________________
"recon" (sic - reckon)(tm) "hihgly"(tm) "seceed"(tm)
"Outback AIDS - Alcohol-Induced Dizzy Spells"
5-90 is offline   Reply With Quote
Unread 06-13-2013, 07:31 PM   #7
leftfield6
Where are my damn keys?
 
leftfield6's Avatar
1964  
 
Join Date: Oct 2005
Location: Beautiful South
Posts: 256
I was able to replicate the "tap healing" by just tapping on the alternator itself. Like someone said upthread, in tapping on the black box, I was essentially tapping on the alternator. I'm going to throw a part at it, and hope for the best. New alternator tomorrow AM, I'll pick up some nylocks and a brass brush, along with a tube of dielectric grease.
__________________
(Current) 98 Grand Cherokee Limited 5.9
http://www.fuelly.com/driver/leftfield6/grand-cherokee

(former) 98 Grand Cherokee Laredo
77 CJ-5
75 CJ-5
leftfield6 is offline   Reply With Quote
Unread 06-14-2013, 05:02 PM   #8
leftfield6
Where are my damn keys?
 
leftfield6's Avatar
1964  
 
Join Date: Oct 2005
Location: Beautiful South
Posts: 256
New alternator. New nylocks. Checked and cleaned all terminals. All good now. Hasn't done the low voltage thing all day. I'm deeming it all good now.

Next thing to tackle will be the growling rear axle.
__________________
(Current) 98 Grand Cherokee Limited 5.9
http://www.fuelly.com/driver/leftfield6/grand-cherokee

(former) 98 Grand Cherokee Laredo
77 CJ-5
75 CJ-5
leftfield6 is offline   Reply With Quote
Unread 06-21-2013, 09:37 PM   #9
tazz33
Registered User
1998 ZJ 
 
Join Date: Sep 2012
Location: Huntsville, Ontario
Posts: 69
Quote:
Originally Posted by leftfield6 View Post
New alternator. New nylocks. Checked and cleaned all terminals. All good now. Hasn't done the low voltage thing all day. I'm deeming it all good now.

Next thing to tackle will be the growling rear axle.
I hear ya there! Mine kinda sounds a bit more from the pass side but not sure yet?
__________________
[COLOR="Black"][CENTER][SIZE="4"][FONT="Showcard Gothic"][COLOR="Black"][URL="http://groups.jeepforum.com/built-not-bought/"][COLOR="Black"]Built Not Bought #679[/COLOR][/URL][/FONT][/SIZE][/COLOR][/CENTER][/COLOR]

[CENTER][B]1998 niner!!!!! K&N, BFG All Terrains, MSD coil, Taylor Thundervolt wires, Superchips Programer, Kolak 3" tailpipe, Magnaflow highflow 3" Cat, MBRP 3" chambered muffler, MBRP 3"-3 1/2" dual wall stainless tip, and gonig to be more to come!!!!![/B]![/CENTER]
tazz33 is offline   Reply With Quote
Unread 06-22-2013, 01:00 PM   #10
HighLonesome
Belief In All Things Jeep
 
HighLonesome's Avatar
1995 ZJ 
 
Join Date: Feb 2005
Location: New Mexico
Posts: 5,563
Quote:
Originally Posted by LeeZJ View Post
I removed that little black box that connects between 2 field coil connections. Had no effect on my charging system.

Lee
I always wondered if there was a diode or a fusible link hidden inside there. The factory diagrams don't even show the black box. Good to know its a static part! And glad the original poster had an easy fix.
HighLonesome is offline   Reply With Quote
Unread 06-22-2013, 01:29 PM   #11
JS97ZJ
Registered User
1997 ZJ 
 
Join Date: Dec 2009
Location: Dingmans Ferry, PA
Posts: 2,035
I had taken mine apart and found a cold solder joint to one of the feild terminals when mine was acting up.
That block has nothing in it. It's just a molded module that holds the wires in the correct place.
JS97ZJ is offline   Reply With Quote
Unread 06-29-2013, 07:22 PM   #12
HandsOn
Registered User
 
Join Date: Mar 2005
Location: San Jose, CA
Posts: 251
Quote:
Originally Posted by JS97ZJ View Post
... It's just a molded module that holds the wires in the correct place.
Kind of a protective "wire strain relief" type of thingy then.
Good to know too, as I was about to start digging into a friend's as well.
I figured with the intermittent nature of the issue, and the occasional moving of objects under the hood, it was seeming less and less likely to be the PCM.

Just like the OP's condition, when it was charging, it would stay charging until you turned the engine off. Then it was back to square one.
Cleaning the engine compartment and re-jiggling things got it working yesterday, but no amount of fiddling after it stopped would get it working again.

I had already almost thrown a new alternator at it, but decided to play detective a little longer before going there. Guess I'll just go for it and help the guy out some more.
Trying anything to avoid the more expensive PCM replacement/fix. I know the fix is cheap, but not feeling like sitting there over a hot soldering iron anytime soon. Rather spend the 100 on a new alternator!
Hmm, maybe a junkyard run? After all, it's only 102 out here today.
But it's a dry heat.

Thanks for throwing some of your money around first leftfield. Time for me to step up and do the same thing...

Paul
HandsOn is offline   Reply With Quote
Unread 06-29-2013, 07:32 PM   #13
HandsOn
Registered User
 
Join Date: Mar 2005
Location: San Jose, CA
Posts: 251
I forgot to ask. Does the standard high output alternator have completely different connections? Or can you still attach the Generator Field Driver Connector (the little black thingy's official name) to the back in the same way?
I was ready to post that up in a separate thread, when I came across yours. I could have compared the two side-by-side in the store, but that would have meant going outside!

And I should ask, does your 5.9 have the 90 amp or the (what?) 116 amp version? Is the black box literally on top of the alt, or down on the back?

Paul
HandsOn is offline   Reply With Quote
Unread 04-23-2014, 12:05 PM   #14
sq5
Registered User
 
Join Date: Apr 2014
Location: anytown, usa
Posts: 5
Alternative (temporary) workaround

I just registered so I could add that I recently experienced the exact same odd problem and symptoms as the OP of this thread.

On mine, I noticed that if I put pressure on the black box towards the front of the vehicle (ie- standing at the front of the vehicle and pulling the black box towards me), the alternator would re-engage with a distinctive whine.

My guess is that it has something to do with the field coil connections inside the alternator.

It's not simply an external contact issue. I too tried cleaning all connections, first with a toothbrush and brake cleaner, and then with a wire brush bit on a Dremel. Ultimately ineffective.

The workaround has been to create a little "harness" of sorts using heat resistant cable ties across the alternator mounts and strapping around the black box as well to apply a constant tension on it towards the front of the vehicle. (I could maybe take a picture or try and draw it if anyone is actually interested.)

As an interesting side note, I was also confused what the black box was until I read here. I saw it called all sorts of things across the web. Does it even have an actual part name or number? How would one even get a replacement of one or its associated cables if needed?
sq5 is offline   Reply With Quote
Unread 04-23-2014, 02:48 PM   #15
ZeeJay1997
Registered User
1997 ZJ 
 
Join Date: Dec 2008
Location: Sweet Home, Alabama
Posts: 6,446
the black box thingy is just a connector. i have seen it called a terminal block. it connects to the field terminals which are part of the brush holder assembly. when you move the connector, it could flex the brush holder enough to disturb the brushes resting position on the slip rings. This is more apt to happen if the brushes are worn. As the bushes wear, it reduces the tension of the spring behind the brushes, thus reducing the force brush of contact with the slip rings.

my solution was to take the alternator out, remove the brush assembly, desolder the brushes, take them to an auto electric shop and get them to match the brushes, solder them back in, put it back together and drive it for another 80K. 1 hour labor and 15 bucks.
ZeeJay1997 is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.