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post #1 of 15 (permalink) Old 03-25-2019, 03:20 PM Thread Starter
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Another not charging

This is for my 1999 3500 auto 4x4

Iím not sure Iím on the right path or not. The voltmeter on the dash shows 8 volts when I first start the truck. After a few seconds it goes only as high as about half way between 8 and 14. I checked voltage at the alternator and am only showing approximately 12.5.

So Iím thinking new alternator but I did a few more tests with my Fluke 117. The AC voltage is 0.03 and I checked the ohms on the blue and green wires between the plug and the pin locations in C2 and C3. One had 1.0 ohms while the other was maybe half that. I also tested the 140 amp fuse in the PDC. It had 0.1 ohms and had continuity. But with the truck running I got zero volts at both the fuse and at the posts where the positive and negative are connected by the fuse.

Do I simply need another alternator? Shouldnít I see voltage at the fuse? My batteries are both about a year old. So is the alternator. Or am I completely missing something else?


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post #2 of 15 (permalink) Old 03-26-2019, 12:31 AM
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The alternator is not charging, either becasue it is bad or the PCM is not properly regulation the alternator. Pull the alt and have it bench tested. If it fails it is bad if it fully passes it is the PCM or its wiring to the alternator plug, including the plug itself. Could easily be either but bad alt is more common.
The 8 volts on start is the grid heaters properly dragging it down, but if the alt was working it wouild recover to 14 not 12.5v, 12.5 is only battery voltage.

99 2500, Quad cab, 4x4 47RE, BD pressure lock on it, small BD 90/140 chip on the VP 44 connection plug, 17" 3rd gen wheels. 3.55 diffs. Ruenell front bumper and warn winch, Rancho adj shocks. 663k miles.
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post #3 of 15 (permalink) Old 03-26-2019, 09:09 AM Thread Starter
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Bigfish, thanks for the information. Thatís what I was thinking as well but itís good to know Iím on the right track. Thanks again for your help.


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post #4 of 15 (permalink) Old 03-26-2019, 12:42 PM
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You may want to rebuild instead of getting one of the poorly remanned alternators sold cheap by the parts stores. Rebuilder in a box has destructions and parts. You definitely want to keep your core until you're sure the replacement is working. People have turned in the core, then gone through multiple alternators without finding a good one then gotten their money back. The problem is their core has been sent away and they can't turn it in if needed when they try another remanned alt.

Test for charging and AC noise before you leave the store when buying any alternator locally. Some fail out of the box.

2000 LWB, Quad Cab, 4x4, NV4500, AirDog, Gauges, Thuren Track Bar, Lost crappy AGR and A1-Cardone steering boxes. RedHead is the best so far but truck has stopped returning to center. Hopefully, I'll get to it soon.
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post #5 of 15 (permalink) Old 07-19-2019, 07:09 PM
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hijack…

I just had my alternator tested at parts store on their machine and it passed as good. Alt was removed from truck of course.

On truck voltage is low, around 11.something at the alternator and similar at the battery when running.

I cleaned one pos battery mount and rechecked. others look fine. I have the battery grease on them.

PCM issues? What is the fix?

So, there are two contacts (not the 12V out) that serve as what-would-be a plug that get bolted to alt with tiny nuts, and a third contact that would only be ground at best, maybe just for stability. On mine the PO had the nut under the thing it was supposed to bolt down. This probably was making ground contact, but maybe something happened, maybe corrosion, where now it was not making good ground to the case.
After getting alternator removed and tested I installed it correctly. I would have done it first, but time and a borrowed car were issues, and alt half off when I realized…
Installed and voltage is up. R and L battery do not match yet, hoping they will after a long charge. Voltage is 13.2 to 13.6 and at 2000 rpm closer to 13,8. I would like to see 14.x at the alternator but am not. Wonder if it is not at 100% output.
Passengers battery is lower voltage even when connected. I cleaned the cable recently, but maybe this is still an outlying issue.

All fuses under the hood seemed fine. There is just the 140amp from alternator and one other fuse related to anything alternator related…

So, this is something to look for, bad contacts on the "plug"
And, my trip tomorrow will tell.

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post #6 of 15 (permalink) Old 07-19-2019, 08:33 PM
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Your alt is not charging. Showing battery voltage only after grid heater goes off. Bad alt or pcm. Remove and have alt bench tested. Test new one for ac below that.03v benchmark.

99 2500, Quad cab, 4x4 47RE, BD pressure lock on it, small BD 90/140 chip on the VP 44 connection plug, 17" 3rd gen wheels. 3.55 diffs. Ruenell front bumper and warn winch, Rancho adj shocks. 663k miles.
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post #7 of 15 (permalink) Old 07-20-2019, 10:38 AM
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Quote:
Originally Posted by andytruck View Post
hijackÖ

I just had my alternator tested at parts store on their machine and it passed as good.

My alternator quit not long ago. The parts store machine said there was nothing wrong with it but it wouldn't charge once installed.

I checked to make sure I was getting a signal from the pcm, which I was, so I ordered a new alternator and all is good.



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post #8 of 15 (permalink) Old 07-21-2019, 03:09 PM
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After correctly installing the pcm connector all is working as it was before. So, that was my issue.
My voltage is high 13's, as it was before, but after reading a lot on here I wonder if this is correct output. Should it ever be over 14v?
Batteries seem happy and crank the starter at the expected speed.
I drove 4 hours already after the fix.

I am working on drudging through info to find out how to test the AC voltage on these to see if it is in spec.
Anyone want to save me some time here?

It is possible the winding can "short" out and still work fine, the "short" only reduces the length of the winding in some cases, so instead of (made up number) 20 feet of copper wire it is 19 feet because the "short" made a short-cut across 1 foot of wire in the middle somewhere. This is a short that does not result in shorting OUT. The short would result in lower voltage, and apparently not that uncommon. The short comes from the coated wire getting warm/hot enough to melt the coating and let the copper touch in a spot or two.
I learned this from an alternator guy, so don't confuse it with my over-all knowledge of things

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post #9 of 15 (permalink) Old 07-22-2019, 12:22 AM
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What are the battery voltages after running for sometime and then disconnected and tested separately? Then leave them disconnected overnight and retest them?

99 2500, Quad cab, 4x4 47RE, BD pressure lock on it, small BD 90/140 chip on the VP 44 connection plug, 17" 3rd gen wheels. 3.55 diffs. Ruenell front bumper and warn winch, Rancho adj shocks. 663k miles.
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post #10 of 15 (permalink) Old 07-22-2019, 09:32 AM
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Quote:
Originally Posted by bigfish95971 View Post
What are the battery voltages after running for sometime and then disconnected and tested separately? Then leave them disconnected overnight and retest them?
Pass 12.44
Drivers 12.55
this is voltage right after separation. Drivers still powering truck.
Today is Monday, n was driven about 4 hrs total on Saturday.

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post #11 of 15 (permalink) Old 07-22-2019, 05:21 PM
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Both are slightly low and not equal. Take them in to a Les Schwab or other good tire shop and have them load tested separately.
If they are being charged well, they are bad. Also check the crossover cable for resistance.
If you have an alternator that is not charging well replace it or have it rebuilt. Don't worry or screw around about broken wingdings. Bad is bad. There is no half way or shorter wire.

99 2500, Quad cab, 4x4 47RE, BD pressure lock on it, small BD 90/140 chip on the VP 44 connection plug, 17" 3rd gen wheels. 3.55 diffs. Ruenell front bumper and warn winch, Rancho adj shocks. 663k miles.
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post #12 of 15 (permalink) Old 07-29-2019, 10:02 AM
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I typically don't take batteries to a tire shop. Do tire people know batteries better?
I am old enough to keep telling people to take car to "gas station" when I really am meaning "repair shop".
Is a "tire shop" an older version of "gas station"?

As long as I have had a good meter on the truck I think the voltage has always said 13.4-13.9 volts when running. I jumps around every few seconds on my Edge. I never thought much of it. Should it ever say over 14? I think 14.7 is the top of the chart, but that would require low voltage batteries to ask that of the alt???

Am I chronically under-charging my two batts at the mid-13's range?

98.5 2500 Extended cab, long bed, 4x4, manual 5-speed.
Edge CS2 31400. FASS 150. 4 inch pipe. Bigger input shaft and output nut, heavy duty clutch, new tranny.
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