Alternator Charging issue

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DigDirt

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I have an alternator charging conundrum on a 1996 M1078 ever since I removed my spare wheel and "cleaned"up behind the cab, the batteries are not charging via the alternator. All I did was relocate the reverse polarity box and remove the ether canister and cut that wire. I've troubleshot the crap out of the alternator, battery connections, etc and only come up with no power on the ENG terminal of the voltage regulator on the alternator (there is 24v to the F- terminal) . So one would think that the regulator is bad, but something doesn't sit right.... could me cutting the ether cable affect the regulator function? Any help would be appreciated.
 

coachgeo

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most common issue of the A0 with charging is the excite wire to the alternator. It round about ways.... sends power to excite the alternator (tells it to start working) from the oil pressure switch only AFTER the engine is running (aka.. high enough oil pressure) . Somewhere in the wiring this gets FUBARed ....... thus the alternator is never told to turn on and charge. Search this forum for POST using terms alternator excite excitation wire charging charge. Should bring up some of the post where this is mentioned.

PS..... after you copy a post you placed elsewhere...... into text box for posting into here...... Highlight it all..... then hit the second button at the top left of the text box [A/A with red X overlay]. This will cancel the black coloring that tends to drive some folk in here a bit nuts
 
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DigDirt

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I will rerouter excitation wire from fuel solenoid as per Supraman's suggestion. What gauge wire is recommended? Also, because all this started after I messed with the reverse polarity box, could that be bad? How do I test it and is it even necessary to have or can it be done away with? Thanks in advance
 

Suprman

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The reverse polarity box is a big diode array. You can test it with a multimeter that has a diode test function or when its in use you can measure voltage in and voltage out. It will drop around 1/3 of a volt at the output. If the polarity box was bad usually you wont have 12 and/or 24 volts at the cab power panel. The alt to batts connection is direct. The alt cables meet the batt cables on the input terminals of the polarity box. The outputs go to the cab panel. What alternator do you have? Is there leds on the regulator? If so what color are they when running?
 

DigDirt

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The reverse polarity box is a big diode array. You can test it with a multimeter that has a diode test function or when its in use you can measure voltage in and voltage out. It will drop around 1/3 of a volt at the output. If the polarity box was bad usually you wont have 12 and/or 24 volts at the cab power panel. The alt to batts connection is direct. The alt cables meet the batt cables on the input terminals of the polarity box. The outputs go to the cab panel. What alternator do you have? Is there leds on the regulator? If so what color are they when running?
There are no LEDs and I think I have the N1506. At least that is what I've been using to troubleshoot; that and the TMs
 

Suprman

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Have you made sure the polarity box wiring is connected correctly first? Make a temp jumper from 24v to the regulator excite terminal and see if it starts making power. The front red connection is the excite. The other regulator connection is a field sense. Dosnt need to be hooked up to function.
 

coachgeo

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I will rerouter excitation wire from fuel solenoid as per Supraman's suggestion....
Have you made sure the polarity box wiring is connected correctly first? Make a temp jumper from 24v to the regulator excite terminal and see if it starts making power. The front red connection is the excite. ....
Will (Suprman) question...... the route you've numerously suggested from the fuel solenoid....... does that route also limit the alternator excitation to only happen after engine is running?
 

Ronmar

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I will rerouter excitation wire from fuel solenoid as per Supraman's suggestion. What gauge wire is recommended?
I would NOT do this. There is a reason it is done the way it is off the oil pressure circuit. These alternators are pretty expensive to replace, so I trust that someone had a good enough reason to do it, like trying to protect the alternator/installing it to manufacturers specs... If the ENG terminal is powered off the fuel solenoid, the regulator will be trying to build maximum field as soon as the switch is turned on, on a non/slow turning alternator that is trying to charge a battery which is trying to power the starter motor...

I would put it on a manual switch before I powered it off the fuel solenoid... Since however it is a fairly simple circuit, if it is not working, I would just fix it so it operates as designed...

The oil pressure sw energizes relay K11 when you turn on the main sw. When the oil pressure sw opens at 15PSI, K11 de-energizes. The de-energized contacts of K11(pin 30-87A) provide 24V from CB77 down to the ENG terminal(TL35) on the voltage reg to turn on the alternator... Thats it...

If for some reason the circuit has an issue, I would pull K11 and install a temporary jumper from 30 to 87A while the engine is running to manually bring the alternator online untill I can repair the circuit. I would remove this jumper while i was starting the engine...
 

coachgeo

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Yup. Fuel solenoid only gets power with the dash switch on. Otherwise your engine wouldnt shut off till it ran out of fuel.
not quit the same... the OEM excite wire does not power the alternator when the engine is trying to be started even though the power button is on.... it only powers it after the engine is running. Sounds like piggy backing off the fuel solenoid works.... just not ideal since it adds strain to starter etc. when starting truck.

oops... see now that Ronmar beat me to it..... and with a far better explanation/solution
 

mechanicjim

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the Niehoff Regulator is actually a little smarter in that when it get Power from its harness and IGN signal from the red terminal it waits till it sees an certain RPM from the alternator phase signal before it powers up the field coil. its call a soft start on some Niehoff units it also ramps up the coil so it doesn't shock load the drive belt.
 

Ronmar

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Some of them are smarter. The N1505-1 and its associated regulator used in the Hmvees has soft start and RPM sense. It also has temperature compensation and over voltage cutout. I believe the N1509 and N1511(used in the A1’s I think) also have these features.

it would be great if it has it, but the The N1506-1 with the N3030 regulator used on the A0’s does not appear to be that sophisticated. No rpm sense, no temp comp or over-volt and nothing I have ever found about a soft start. It only has output current limitation in any of the documentation I have seen.
 

DigDirt

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Have you made sure the polarity box wiring is connected correctly first? Make a temp jumper from 24v to the regulator excite terminal and see if it starts making power. The front red connection is the excite. The other regulator connection is a field sense. Dosnt need to be hooked up to function.
I am pretty sure that it is wired correctly in that I labelled the wires before I relocated the box. That said, I have wired it opposite to what it is now to ensure completeness and the engine wouldn't start..,IMG_20191110_144411.jpg
I will make a temp jumper from the 24v on the polarity box to the ENG terminal this weekend. That is a great suggestion! Thanks.
 

DigDirt

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the Niehoff Regulator is actually a little smarter in that when it get Power from its harness and IGN signal from the red terminal it waits till it sees an certain RPM from the alternator phase signal before it powers up the field coil. its call a soft start on some Niehoff units it also ramps up the coil so it doesn't shock load the drive belt.
I don't think mine is that smart....rofl
 

DigDirt

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I would NOT do this. There is a reason it is done the way it is off the oil pressure circuit. These alternators are pretty expensive to replace, so I trust that someone had a good enough reason to do it, like trying to protect the alternator/installing it to manufacturers specs... If the ENG terminal is powered off the fuel solenoid, the regulator will be trying to build maximum field as soon as the switch is turned on, on a non/slow turning alternator that is trying to charge a battery which is trying to power the starter motor...

I would put it on a manual switch before I powered it off the fuel solenoid... Since however it is a fairly simple circuit, if it is not working, I would just fix it so it operates as designed...

The oil pressure sw energizes relay K11 when you turn on the main sw. When the oil pressure sw opens at 15PSI, K11 de-energizes. The de-energized contacts of K11(pin 30-87A) provide 24V from CB77 down to the ENG terminal(TL35) on the voltage reg to turn on the alternator... Thats it...

If for some reason the circuit has an issue, I would pull K11 and install a temporary jumper from 30 to 87A while the engine is running to manually bring the alternator online until I can repair the circuit. I would remove this jumper while i was starting the engine...
fair enough. Certainly sage advice Ronmar, however, I first need to be sure that the regulator isn't bad (which is the conclusion according to the flow charts after my extensive troubleshooting). Once I know that the regulator is OK, then I plan to jump K11 30 to 87A until I figure out where the problem in the circuit is...... Does that sound logical to yáll?
 

Ronmar

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As long as everything is wired to spec(TL35 to ENG on regulator)yes, jumping the K11 contacts should energize the alt. Measuring the 12 and 24v Test points at the PDP should show you if the polarity box is wired correctly...
 

DigDirt

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Well I repeated all the troubleshooting gymnastics and again came to the conclusion the voltage regulator is bad. Does anyone have or know where I can get one of these? Niehoff dual voltage regulator 76761-n3030
 

coachgeo

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might be less/just as expensive to replace whole alternator with a 200amp from a Hummer. (appears to be only model beside fmtv version that can fit in the space).
 
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