Alternator(s) voltage too high, intermittent - Diesel Forum - TheDieselStop.com
E-Series Vans Technical discussion of topics related to vans powered by any of the Navistar engines. This covers a broad number of years, but there isn't enough demand to split it any further.

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post #1 of 17 (permalink) Old 03-08-2018, 03:36 PM Thread Starter
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Alternator(s) voltage too high, intermittent

Hi,
Today I drove the van about 120 miles. After a couple of hours of driving, the volt meter pegs @ 18 volts.
Then wiggles around for a while, then goes back down to normal.
A few miles later, repeats.
Not sure if there is AC in the DC voltage, am going to measure that, somehow, which would indicate one or both full-wave bridge rectifiers have leaking diodes.
The van has dual alternators, recently replaced both of them w/ Carquest rebuilt.
Problem solved for a few months, now it is back.

Is there any other system or component that regulates alternator DC voltage output, other than the built in voltage regulator in each alternator?

If there is no external voltage regulation, I might have to replace the alternators again, but with a better brand, new, not rebuilt this time.
Top alternator is a 10 minute job.
Bottom alternator is all day, remove radiator, fan/clutch assy, an idler pulley, etc.

2000 E350, I ordered it from the factory, new. Dual A/C, XLT Super Duty trim, 3.55 limited slip, trailer tow class IV package, dual alternators,
speed control/tilt wheel, HD4R100 installed @203k miles, B&M cast pan,
Dahl 100 fuel filter, deleted stock fuel bowl drain valve (leaker),
replaced turbo pedestal w/ non-EBPV, deleted AIH. Bilstein shocks. Jensen VX7021 Navigation receiver, Garmin 65W dash cam
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post #2 of 17 (permalink) Old 03-08-2018, 04:54 PM
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Quote:
Originally Posted by tcnofh1 View Post
The van has dual alternators, recently replaced both of them w/ Carquest rebuilt.
Why? What exactly was wrong with the previous alternators?
Quote:
Originally Posted by tcnofh1 View Post
Problem solved for a few months, now it is back.
Then it wasn't solved. If this symptom was the reason you changed the original alts, then you just masked it by unnecessarily changing some parts.
Quote:
Originally Posted by tcnofh1 View Post
Is there any other system or component that regulates alternator DC voltage output, other than the built in voltage regulator in each alternator?
Not in the way you mean, but yes: the entire charging system (every little component) affects the charging voltage. A poor connection (high resistance) anywhere can cause voltage variations across the system. Variations in some places can cause the VR to go to full-blast (like you're describing).

You have to understand that the whole system (battery, cables, connectors, fuses, alternator, wiring harness...) either works together as-designed, or it DOESN'T work. And just because it's not working, you can't arbitrarily focus on the alternator, and expect to solve the problem.

When you had the alternators out, did you look at their mounting surfaces? Were they all shiny-clean flat metal? Or were they greasy, rusty, paint-flaky catastrophes? All the current that the alternator is trying to make has to pass from the alternator case, to the engine, to the ground cable, to the battery negative terminal(s), to the battery(ies), to the positive terminals, to the hot cable, to the alt fuse, to the alt cable, to the alt output post. A poor connection ANYWHERE along that circuit will inhibit the system from working properly. Click each of these & read all their captions:


(phone app link)



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(phone app link)
Quote:
Originally Posted by tcnofh1 View Post
...I might have to replace the alternators again, but with a better brand, new, not rebuilt this time.
Even if you can find a truly "new" alternator (which I doubt), there's nothing different about how it's built vs. a reman. Their parts are tested the same way with the same equipment, and it's at least as likely (if not moreso) to get a bad NEW part as a used one that fails sometime between testing & installation. CQ might not be the best that can be had, but they're certainly good enough to assume (for a while) that your problem is elsewhere.


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Last edited by Steve83; 03-08-2018 at 04:57 PM.
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post #3 of 17 (permalink) Old 03-09-2018, 07:49 AM Thread Starter
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Hi Steve,
The original alternators had shorted diode(s) in the bridge rectifier, causing current draw when the van was powered off.
I'll try cleaning the negative chassis grounds.
Going to get rid of the dual alternator solution, it has been more trouble than it is worth.
Installing a single, new, Leece Neville alternator on top, disconnecting the lower alternator.
Frank

2000 E350, I ordered it from the factory, new. Dual A/C, XLT Super Duty trim, 3.55 limited slip, trailer tow class IV package, dual alternators,
speed control/tilt wheel, HD4R100 installed @203k miles, B&M cast pan,
Dahl 100 fuel filter, deleted stock fuel bowl drain valve (leaker),
replaced turbo pedestal w/ non-EBPV, deleted AIH. Bilstein shocks. Jensen VX7021 Navigation receiver, Garmin 65W dash cam
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post #4 of 17 (permalink) Old 03-09-2018, 09:53 AM
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Why don't you disconnect the alternators, one at a time, and see if the issue goes away.

2000 F250 Lariat CC SB 4x4 PSD Auto
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post #5 of 17 (permalink) Old 03-09-2018, 04:18 PM Thread Starter
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Yes, I will do that.
In the past I have run it w/ the lower alternator B+ disconnected, while waiting for a schedule to replace it (shorted).

Talked to an alternator place, there is a wire that feeds the "sense" circuit of these alternators.
If I can find which wire(s) are involved, might just be an intermittent connection.

Found that with the 6.0 PCM, on the dual alternator trucks, the PCM switches between the two alternators from time to time (not sure what triggers the switch).

Since my charge voltage stays good for a long time while driving, then switches to 18+ VDC, then switches back to 13.8, the 7.3 PCM might also have some
kind of switching going on.

So I'll disconnect the lower B+ and drive it 100 miles and see.

Did more investigating (FICMRepair.com), the Leece Neville option might not work due to the size of the alternator.
It comes with longer mounting bolts, and there is not that much clearance for the stock top alternator to begin with, not sure if I want to be the test case.

2000 E350, I ordered it from the factory, new. Dual A/C, XLT Super Duty trim, 3.55 limited slip, trailer tow class IV package, dual alternators,
speed control/tilt wheel, HD4R100 installed @203k miles, B&M cast pan,
Dahl 100 fuel filter, deleted stock fuel bowl drain valve (leaker),
replaced turbo pedestal w/ non-EBPV, deleted AIH. Bilstein shocks. Jensen VX7021 Navigation receiver, Garmin 65W dash cam
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post #6 of 17 (permalink) Old 03-09-2018, 11:36 PM
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Based on the wiring diagrams here:
BBB Industries- Premium Alternators, Starters, Power Steering Products | TSB's & Wiring Diagrams (you don't have to use a real e-mail to get in)
http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=18444
...it looks like the PCM can connect one or both "I" circuits to the key-switched dash light (12V) so that each alternator behaves just like a single would.

But the single appears to use a 3G.
http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=18445


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post #7 of 17 (permalink) Old 03-14-2018, 06:24 PM Thread Starter
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Found some good info today.
Scanned the codes, P1160 lower alternator fault.
Disconnected lower alternator B+
Took the van for a 130 mile highway drive.
Voltage and current normal!

Looked at the schematics for single & dual alternators via the links Steve83 sent, hoping to
see a way to convert the wiring from dual to single.
Later on, I was able to regain consciousness, determined that I will NEVER be able to figure that out.

SO
If I leave the lower alternator in place, B+ disconnected, small wires connected, possibly the PCM will not freak out.
I could install a “single alternator” serpentine belt, rendering the lower alternator inert but in circuit.

2000 E350, I ordered it from the factory, new. Dual A/C, XLT Super Duty trim, 3.55 limited slip, trailer tow class IV package, dual alternators,
speed control/tilt wheel, HD4R100 installed @203k miles, B&M cast pan,
Dahl 100 fuel filter, deleted stock fuel bowl drain valve (leaker),
replaced turbo pedestal w/ non-EBPV, deleted AIH. Bilstein shocks. Jensen VX7021 Navigation receiver, Garmin 65W dash cam
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post #8 of 17 (permalink) Old 03-15-2018, 10:20 PM
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I'd unplug the lower alt's VR. One of its small wires (the one at the "A" terminal) is also B+, so if you're abandoning it, you don't want a later failure to kill the batteries or start a fire.

The wiring for the 2 alts isn't much more than the single alt's wiring, repeated. Removing either one will make it a single-alt system. You'd want the LG/R wire from the dash/PCM to go directly to the working alt's "I" terminal (like the single). You'd DISconnect the dead alt from S178. And you'd DISconnect the dead alt's Bk/Or output wire from either S1011 (if primary is dead) or the starter relay (if secondary is dead).

That's what the last link shows, for the factory single alt.


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post #9 of 17 (permalink) Old 03-21-2018, 07:16 PM Thread Starter
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"Nothing difficult is ever easy", I wise person once told me.

Tried to install a serpentine belt for a single alternator system today.
Won't work, part of the bracket holding the lower alternator interferes with
the path of the serpentine belt.
So I'll be pulling out the radiator and related parts to get to the lower alternator and the giant bracket holding it.
Will try to remove it all.

2000 E350, I ordered it from the factory, new. Dual A/C, XLT Super Duty trim, 3.55 limited slip, trailer tow class IV package, dual alternators,
speed control/tilt wheel, HD4R100 installed @203k miles, B&M cast pan,
Dahl 100 fuel filter, deleted stock fuel bowl drain valve (leaker),
replaced turbo pedestal w/ non-EBPV, deleted AIH. Bilstein shocks. Jensen VX7021 Navigation receiver, Garmin 65W dash cam
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post #10 of 17 (permalink) Old 03-21-2018, 10:29 PM
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Could you remove that alternator & fabricate and install a bearing pully/idler?

1999 E350 7.3psd , XLT , 15 pass/ext , purchased 6/6/05 w/255k on odo, 8/05 added BTM/straight pipe,5/06 BTS,1"shimmed front coil springs,Michelin XPS 235/85 16 R.,FredGroeske2"rear wheel spacers,1-1/2" rear sway bar,AIC,3 A-pillar guages, Tekonsha envoy,coolant filter,4 pos dp-tuner,In-tank mod & harpooned,dahl-100 prepumpfilter,Scan-guage,Bilstein shocks.
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post #11 of 17 (permalink) Old 03-22-2018, 12:01 PM
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The dead alternator will work as an idler. Don't do negative work removing it, unless you're going to install a good one. And don't throw good money away on something else (an idler) that doesn't do anything for your van. Put a dual belt on it, unhook the wiring where it's easy to access (& repair later, if you or a future owner chooses to), and drive it.


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post #12 of 17 (permalink) Old 03-27-2018, 03:55 AM
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Im thinking your alternators are fine and your batteries are the problem.
Have you disconnected them and tested the resting voltage?
I have dual alternators on my 7.3 and its great.

Btw how are you testing the voltage?

Name: Rob.
Current:
2001 E350 EB HT PSD w/ a bunch of stuff.
Had three other E350s...
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post #13 of 17 (permalink) Old 03-27-2018, 09:16 AM Thread Starter
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Batteries are new, don’t see how a battery can cause the lower alternator to put out over 18 volts.
Disconnected and removed the lower alternator, now running on the top alternator only, batteries charge normally, charging voltage about 14.

2000 E350, I ordered it from the factory, new. Dual A/C, XLT Super Duty trim, 3.55 limited slip, trailer tow class IV package, dual alternators,
speed control/tilt wheel, HD4R100 installed @203k miles, B&M cast pan,
Dahl 100 fuel filter, deleted stock fuel bowl drain valve (leaker),
replaced turbo pedestal w/ non-EBPV, deleted AIH. Bilstein shocks. Jensen VX7021 Navigation receiver, Garmin 65W dash cam
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post #14 of 17 (permalink) Old 03-30-2018, 04:40 PM
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Ok, you got it.

Name: Rob.
Current:
2001 E350 EB HT PSD w/ a bunch of stuff.
Had three other E350s...
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post #15 of 17 (permalink) Old 03-30-2018, 07:37 PM Thread Starter
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Going to try something new, now that the van is operating on one chinese rebuilt alternator.
Bought a Leece Neville alternator.
It has more amps output than the stock 110A unit.
The van is stock, don’t really need more amps, but trying to find a NEW, not rebuilt, not chinese alternator is a pain.
The L.N. is a new unit, will install it soon and see how it does.
I have read and fully understand the warnings about a higher amp output alternator damaging the glow plugs.
Have a plan to deal with that, no worries.

2000 E350, I ordered it from the factory, new. Dual A/C, XLT Super Duty trim, 3.55 limited slip, trailer tow class IV package, dual alternators,
speed control/tilt wheel, HD4R100 installed @203k miles, B&M cast pan,
Dahl 100 fuel filter, deleted stock fuel bowl drain valve (leaker),
replaced turbo pedestal w/ non-EBPV, deleted AIH. Bilstein shocks. Jensen VX7021 Navigation receiver, Garmin 65W dash cam
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