Location of grounding strap(s)

dgeist · **Posted:** Mon Dec 14, 2015 9:55 pm

I'm troubleshooting an inconsistent voltage level in my lighting system (causing flickers) The alternator and battery have already tested good under load. Can someone point me to the location of the grounding strap(s) between the block and the body? I'd like to see if one's possibly loose causing my issues.

Dan

flash7210 · **Posted:** Mon Dec 14, 2015 10:08 pm

What kind of flickering lights are you experiencing?
About a week ago I was experiencing a similar thing. Rapidly flickering headlights at about 1200 rpm accompanied by a slight engine stumble.
I checked all my wiring connections and all were tight. Maybe it was the voltage regulator?
Anyway, that seems to have gone away for some reason. At least for now.

If you really think its a ground strap, add your own for a test.
Attach a wire from a bolt on the alternator bracket to the negative side of the battery and see what happens.

Mountainman · **Posted:** Tue Dec 15, 2015 12:52 am

What Flash said is easiest, but the two ground leads land on a large stud just in front of the starter.
It think there's one or two up on the frame for the dash also. Oh, and then there's one under the console, and one or two in the back of the rig also.

dgeist · **Posted:** Tue Dec 15, 2015 10:39 am

I guess the "test" I had done should be viewed with a grain of salt. It was at an Advance Auto Parts...

The symptoms are both interior lights and headlights flickering slightly whenever on (but more noticeable just after start at idle). There does appear to be a bit of additional engine "loading" during the time, and I suspected the regulator function as well.

I'll try the disconnect a bit later, but need to find a dark place to do it (parking garage, perhaps...).

Dan

olypopper · **Posted:** Tue Dec 15, 2015 1:54 pm

You can also place a digital multimeter on your your battery and test for A/C voltage presence. If there is more than approx. .15 volts of A/C voltage it could mean a bad diode in the alternator's rectifier/regulator.

dgeist · **Posted:** Tue Dec 15, 2015 3:19 pm

olypopper wrote:

You can also place a digital multimeter on your your battery and test for A/C voltage presence. If there is more than approx. .15 volts of A/C voltage it could mean a bad diode in the alternator's rectifier/regulator.

Good info. I'm perfectly happy doing tests with my Fluke

Dan

dgeist · **Posted:** Sat Dec 19, 2015 11:08 am

(Possibly) good news. I did some basic tests and here's my results with the voltmeter:

14.3-14.6 VDC (varrying) - Vehicle running with lights (flickering)

- remove voltage regulator plug from alternator assembly

11.9 VDC - vehicle idling with lights (no flicker)
12.1 VDC - vehicle idling, no lights
12.4 VDC - vehicle off

So, I ran it for about a day with no regulator plugged in and things worked fine. I put it back in this morning and tested and got the following:
14.01 VDC - Vehicle running with lights (no flickering)
.015 VAC (very acceptable).

I'm thinking I just had a loose/wet/slightly corroded contact on the plug and removing it and replacing it a day later may have solved the issue. Now to put a little dielectric on that bad boy so it doesn't happen again.

Dan

flash7210 · **Posted:** Sun Dec 20, 2015 8:26 am

Last night my lights were doing the flickering thing again while driving home.
So I stopped and unplugged the single wire to the regulator on the alternator and sure enough the flickering stopped.
I'm surprised that the alternator still works with that wire unplugged.
I didnt do any voltage checks with it like that but everything worked fine for the rest of the drive.
There is probably the chance of the battery getting overcharged in this state so long drives like this would not be reccomended.

fratichelli · **Posted:** Sun Dec 20, 2015 9:31 am

Technically, the alternator doesn't work with the regulator wire unplugged. Your post even shows you're just running off of battery power.

Sounds to me like you need a new alternator, or your computer has a bad circuit. I am pretty sure the charging circuit does include a voltage regulator in the computer.

thermorex · **Posted:** Sun Dec 20, 2015 10:59 am

fratichelli wrote:

Technically, the alternator doesn't work with the regulator wire unplugged. Your post even shows you're just running off of battery power.

Sounds to me like you need a new alternator, or your computer has a bad circuit. I am pretty sure the charging circuit does include a voltage regulator in the computer.

I agree with this. That Small gauge wire is what provides current to the electromagnet (stator), so when the rotor moves, generates Ac current. The stator does not have permanent magnets (earth magnets), so it needs electricity to energize and produce magnetic field. When disconnecting that wire, the stator will have no magnetic field, the rotor just spins without generating current, and the bcm (I think it's bcm not ecm but not sure) is cutting power to it to prevent battery overload and/or load when alternator current is not needed (thus it has that decoupler, to smoothen up the shock when the stator is "energized"). Light flickering is usually caused by shot diode(s) used to transform Ac current to DC and prevent backfeed. I also had an issue when the lights were flickering, replacing the alternator fixed the issues.

flash7210 · **Posted:** Sun Dec 20, 2015 11:33 am

What you say about the alternator and regulator wire makes sense. And if true, thank god I have a really good battery. Otherwise I don't think I would have made it into work early this morning.

But there are such things as "one-wire" alternators that are not permanent magnet.
There is a fairly common modified GM alternator that has a built in regulator and has only one wire attached to it. It's very common for hot rodders to use this because it cleans up the look of their engine.
Even on my old mustang with the external regulator I added a small regulator circuit that attached to the posts on the backside of the alternator. This converted the stock alternator to a "one-wire" alternator.

I believe what you say is true about the CRD alternator. It doesn't make sense for it to function without that wire connected. None the less, I will do some voltage tests to try and confirm what is actually happening with the charging circuit.

fratichelli · **Posted:** Sun Dec 20, 2015 12:33 pm

How old is your alternator? I had a similar problem and then a year later the same problem. I did all of those tests and couldn't make a clear determination so I just did what dealers did, KGP swap (known good part) and I was good for a year. Then I put another one on and it died in a few days.

Turns out you can't trust rebuilt alternators from Autozone/Advanced etc. But after I got a reliable rebuilt from a mechanic and a decent battery I've been trouble free.

thermorex · **Posted:** Sun Dec 20, 2015 12:50 pm

My alternator issue happened on a pos advance auto rebuilt. I got it since the oem had a shoot decoupler. After about 4 months, I noticed the flicker. Meantime, I got a spare decoupler and the proper tools to replace the oem decoupler. I swapped the oem with the rebuilt and it is still running fine w/o issues.

flash7210 · **Posted:** Mon Dec 21, 2015 11:36 am

So, there are two wires connected to the alternator.
A large gauge wire connected to battery + voltage.
And a small gauge wire that presumably is for the voltage regulator.

Well I dont know what that small gauge wire is for but I have confirmed that having it unplugged does not effect the function of the alternator.
Here are my test results:

Battery voltage= 12.18v with key off and no load
Battery voltage= 11.46v with key ON, headlights on, fog lights on, and fan on high
Alternator ouput= 14.04v with engine running at idle, all lights on, fan on high, and regulator(?) wire unplugged
Alternator ouput= 14.04v with engine running at 2000 rpm, all lights on, fan on high, and regulator(?) wire unplugged
Alternator ouput= 14.04v with engine running at idle, all lights on, fan on high, and regulator(?) wire plugged in
Alternator ouput= 14.04v with engine running at 2000 rpm, all lights on, fan on high, and regulator(?) wire plugged in

So, as long as the engine is running and that large gauge cable is attached to the alternator, the alternator will charge and regulate itself.
I dont know what the small gauge wire is for, but having it unplugged fixes the flickering light problem. Everything functions just fine with it unplugged.

fratichelli · **Posted:** Mon Dec 21, 2015 7:18 pm

I just looked at page 2104 of the KJ 2006 shop manual and it shows that that wire (BR/DG) goes to the Generator Field Control circuit in the Module - Body Control for Diesels.

It's not supposed to work without the wire, but the proof of the pudding is in the eating. Too bad we don't have a voltage gauge on these things anymore. Maybe you can hook one up. If it works - it works, I can't really argue with that. All I know is that on my gasser it didn't when I unplugged it and I thought that is what I read when I looked at your numbers, but I see that I read wrong.

thermorex · **Posted:** Tue Dec 22, 2015 12:25 am

There are voltmeters with cigarette lighter sockets (12v) available for this, just to check the functionality.

flash7210 · **Posted:** Tue Dec 22, 2015 10:58 pm

Well, I am no longer convinced that unplugging that wire on the alternator fixes the flickering light problem.
The flickering light thing is definitely intermittent. I wish I could figure out what causes it and why.
Obviously, the only time it is noticable is at night. Driving during the day, there is no indication that there might be any kind charging or electrical problem.
And at night with the lights on, the flickering doesnt always happen.
And when testing during the day with lights on, the flickering doesnt always happen.
Every test I have done indicates that the alternator is working great.

thermorex · **Posted:** Wed Dec 23, 2015 1:50 am

Flash, why don't you get a new alternator from Autozone and see what happens with it? You can always return it back for a full refund. I think it's worth imo.

fratichelli · **Posted:** Wed Dec 23, 2015 5:21 am

Thermorex, I had an alternator from those cheap stores fail right out of the box. Seems remanufacturers are simply cleaning and painting them.

Known good part testing only works when you have a known good part.

flash7210 · **Posted:** Wed Dec 23, 2015 8:04 am

Looks like repair parts are availabe
https://www.aspwholesale.com/repair-kit-nd-ir/if-150a-p8455.html

Location of grounding strap(s)

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