[Bob7.3]

John, I think we're on the same page; my "output lug" = your "Alternator Positive Post." To be clear, it's not the sense wire that connects inside to the regulator (which, being high-resistance should only carry minimal current at any time), or the on/off wire that powers up the device through the ignition switch.

Many posts around the web mention this approx 1.1 A leak. At least one dedicated soul took his entire electrical system apart and still couldn't identify the source. (How many others have done similar unknown to the public?)

Here's another piece of the puzzle: About a week after installing a new alternator (which happened right after vehicle purchase), I noticed the leak was present. Was it there immediately after the new alt install? IDK because who checks for key-off current leaks when the new equipment works fine. In any case, this could indicate a fairly common problem with aftermarket regulator packs, even high-end ones (mine wasn't but your MM was).

So this bedeviling problem only has a workaround for now; the one you mentioned with a relay. That will take care of half the leak. You're the only one (I've found in wide web searches) to identify the welded relay contacts in the cluster as the source of the other half. Many thanks for that.

Wish I had more tolerance for working on these things in winter, I'd be out there checking this now. It's not just that a good whack hurts several times more than in normal temps, but if it's less due to hands being totally frozen, then the pain is even worse when they thaw. Bleh, too old for that.

 

[John in OkieLand]

If the temp climbs over 43-45 then I will be outside working on this issue.
I am a bit pissed that MechMan still has not replied to my email of last Monday, this is Friday.

I intended to call them today, but I forgot about it... need to set an Alarm on my phone for Monday to make that happen

This is Just Not Acceptable.

Here is a video by a Ford Dealership Technician who knows his Sh*t
He is lambasting Ford for not fixing this Known Alternator Problem for more than 20 years, even before that, He Identified it in 2000.....

Somewhere, he mentions that one the auto manufacturers were using Single Wire Alternators, this problem did not Exist. It started when they decided to have the ECM command the Alternator output... what a farce.

He had put on up to 6 Alternators on one of the cars he worked on, and that is just one.
He keep seeing cars come into the Dealership with Alternator problems that Cannot be Fixed. No amount of OEM Reman Alternators will fix the problem.

Once, an Alternator from AutoZone was the solution on one car, but even that was a Pig in a Poke.

Tmw, I plan on removing the rubber plug from the Vehicle harness on the Alternator, then reattaching the 2-O Cable from the battery to the Alternator output Stud.... and measure the Parasitic Draw under that Scenario.

 

[Big Horn]

Not sure I completely agree with the tech on that video. He doesn’t mention diesel vehicles and the glow plug system, but instead is referencing gas engine vehicles. It is my understanding that in “our” trucks the PCM needs to monitor the alternator so as not to damage the glowplugs which is why the alternator doesn’t begin charging until after the GPR cycles off. Also, even after going to aftermarket alternators he had to swap out 3 or 4 before getting a good one? If the fix is to keep changing alternators until you find one that works how is that the fault of engineering on the charging circuit when no other changes were made other than swapping alternators. I’m not arguing theirs an issue, just having trouble wrapping my head around the actual cause. Thanks for the video John - hope you get it figured out👍

 

[John in OkieLand]

Glad you mentioned that the Ford Diesels are not supposed to start charging until AFTER the glow plugs are OFF.

I need to verify that is true on my truck, as the Alternator was installed at a diesel repair facility in Price, Utah. They told me that they had to call the manufacturer "MechMan" to verify how to wire it to the Harness, as the colors do not match up at all.

 

[bugman]

I'm tagging @ford_doctor to see if he can help on this thread as far as how the alternator is suppose to work on your year of truck.

I know on our OBS trucks the alternator is running all the time that the belt is turning, but it can't keep up with the glow plug draw so it looks like it just starts charging once the plugs shut off.

 

[Big Horn]

John, I may have misstated... ? I’m posting the thread below that I remembered when I was considering a high output alternator, and then changed my mind because of the glowplugs.
Maybe the PCM doesn’t turn off the charging but instead the glowplugs use the majority of the Alternator output as bugman stated........I don’t know but will be interesting what ford_doctor has to say.

Either way, this thread I’m attaching brings up some interesting points, Glenn :

Any issues with higher output alternators?

Just curious if anyone could tell me if I would have any issues with upgrading to a slightly higher output alternator in place of a stock one in a '02 7.3 f250. I was thinking about a 185 or 190 amp from DC Power when I do upgrade. Thoughts anyone? Thanks.

www.thedieselstop.com

 

[Oneof6]

Glad you mentioned that the Ford Diesels are not supposed to start charging until AFTER the glow plugs are OFF.

I need to verify that is true on my truck, as the Alternator was installed at a diesel repair facility in Price, Utah. They told me that they had to call the manufacturer "MechMan" to verify how to wire it to the Harness, as the colors do not match up at all.

I posted the attached PDF of a start voltage timing test recently. The file depicts in spectra, voltage vs time, two different starts, one very cold, one engine at normal full temperature. I didn't note then that the IAH heater is deleted. That actually makes the test data cleaner for a GP timibg determination.
On the cold start it appears to me that the alternator starts to contribute voltage at the engine start, a full minute before the GP's kick off.
I don't have the same alternator my truck has a 6G big case alternator for a 6.0L fit into where the OEM smaller case original was. Bought it at O'Reilly. Did a cable upgrade when I installed it.

 

[John in OkieLand]

I posted the attached PDF of a start voltage timing test recently. The file depicts in spectra, voltage vs time, two different starts, one very cold, one engine at normal full temperature. I didn't note then that the IAH heater is deleted. That actually makes the test data cleaner for a GP timibg determination.
On the cold start it appears to me that the alternator starts to contribute voltage at the engine start, a full minute before the GP's kick off.
I don't have the same alternator my truck has a 6G big case alternator for a 6.0L fit into where the OEM smaller case original was. Bought it at O'Reilly. Did a cable upgrade when I installed it.

Thank you for that PDF.
I have a very old Phillips 200 mHz 2 channel Oscilloscope, left over from my Electronics Servicing days..... almost threw it in the trash, because it has not been used since 1998.
Lost the Cables to it.


But, for DC Voltage test, all I need is a BNC connector and two wires.
I will drag it out, clean off the 'Mouse Dust" and set it up, and take some Pictures after it get it hooked up to my '02 Excursion.

again, Thank you.

 

[klhansen]

The alternator on the single generator installation is NOT controlled by the PCM. See the attached charging system diagram and note that there's no connection to the PCM shown. The second alternator (buried down on the passenger side of the engine) IS controlled by the PCM, although I don't know when it's turned on or off, maybe if voltage sensed by the PCM goes lower than a certain value.

 

[John in OkieLand]

Rained all day, supposed to be dry and 44*F Sunday,
will get a look again, and see what I can correlate with that Schematic.

tnx.

 

[ford_doctor]

I'm tagging @ford_doctor to see if he can help on this thread as far as how the alternator is suppose to work on your year of truck.

I know on our OBS trucks the alternator is running all the time that the belt is turning, but it can't keep up with the glow plug draw so it looks like it just starts charging once the plugs shut off.

You need to be specific on what model year 7.3L engine - there are several different configurations across the pickups, Econolines and Excursions. I am not sure at this point which truck we are diagnosing.

 

[John in OkieLand]

You need to be specific on what model year 7.3L engine - there are several different configurations across the pickups, Econolines and Excursions. I am not sure at this point which truck we are diagnosing.

this is My Thread, and truck is in my Signature and Avatar.

 

[John in OkieLand]

the Mystery has been SOLVED.

the diesel shop reversed the Sense wire, and the Light Circuit wire to the truck's harness.

a phone conversation with the MechMan support person, " Richard " when I told him what was happening, he asked me to pull the Rubber Connector out, and measure the voltages.
he said it was an easy mistake for those unfamiliar with the Ford wiring harness.

the Diesel Repair shop's mainstay is Kenworth, PeterBilt, and Mack trucks.

MechMan is sending me out a new Rubber Connector, because the diesel shop mechanic cut the wires to damn short to the rubber plug, for me to be able to reverse the wires, and solder, and heat shrink again.

the Sense Wire, key off, is supposed to be near Zero volts.... it was 12.8, V or battery voltage as the Battery Tender is wired full time. ( to keep the Parasitic Draw under control )

now I can forget about a Kludge Relay to open the Alternator output....

the Parasitic Draw is now 0.055 to 0.060 or 60 mA on the Passenger side of the truck.

On the Driver side, with the Alternator's Stud connected to the Battery, but the Sense Plug is removed... the draw is now Zero milliAmps

 

[Oneof6]

Great news, that makes perfect sense.

 

[klhansen]

You should be able to remove the pins from your plug and reverse them. There's a red plastic piece in the face that you can pull out with a pick, and then release the pins by reaching inside with the pick to move the latches back and then pull the wires out the back of the plug. Pretty easy to do once you figure out how.

 

[Big Horn]

Great news!

 

[John in OkieLand]

You should be able to remove the pins from your plug and reverse them. There's a red plastic piece in the face that you can pull out with a pick, and then release the pins by reaching inside with the pick to move the latches back and then pull the wires out the back of the plug. Pretty easy to do once you figure out how.

the rubber plug has the wires Epoxied to the backside from the Factory.
they did not want any water intrusion, pins backing out of the holes.

in an Emergency, i could just snip the splice out, and slide Shrink Tubing over the Ford side of the wires, do an AT&T telco twist, and solder the wires... slip shrink, and heat gun it...

but, they offered me a new plug, already got the Email saying it is on the way...
gives me 5 inches of pig tail to work with. that makes me happier, as I can now Zip Tie the wire loom so it don't flop around.

 

[klhansen]

Yeah, if someone glued the wires in, then you're stuck with a new connector and splicing.

 

[John in OkieLand]

Closing Thread, for all intents and purposes.

The new MechMan adapter harness arrived today.
It is configured as a " Plug 'n Play " for the OEM wiring harness,
but alas, someone cut off the OEM connector,
so, I had to do the Twist lock and tape for a Temporary Test setup.

The old 14.85 volt output all the time, disappeared.
it is now regulating at 12.6 volts on a warm day,
the same exact voltage that the Delran Battery Tender was floating at when I opened the hood.

The Clamp On Ammeter is now showing 50-60 mA Parasitic Draw to the Alternator output cable.

The passenger side OEM harness draw changed, from the 60 mA with Alternator unplugged, to 120 mA draw with the Alternator's harness plugged in.

Logic says that is correct,
1) 60 mA for the truck key off
2) 60 mA for the Alternator key off
total =120 mA

that is a huge improvement from the 1.1 amps draw when I bought the truck.

Now, I can go to sleep, knowing that the truck will start next week, or next month w/o being plugged in.

 

[John in OkieLand]

It is my understanding that in “our” trucks the PCM needs to monitor the alternator so as not to damage the glowplugs which is why the alternator doesn’t begin charging until after the GPR cycles off.

I wanted to let all know how the properly wired up MechMan 320A alternator performed after start.

the Digital DVM showed 12.55 ish, key off, no charger attached.
I unplugged the Battery Tender before starting.

WTS went off, waited 30 seconds, and started engine.

Battery voltage dropped to 12.1 volts for a good long time, wish I had timed it.
was not expecting to see what I did.

About 2 minutes or more, after engine start, the voltage started Ramping Up fast, and settled out at 12.66 volts, and stayed there for a full 10 minutes with engine idling.

So, your statement, that I highlighted, is FACT.
Ford prevents the Alternator from kicking in, until AFTER the Glow Plugs are OFF.

This tells me, that I have stressed those glow plugs a lot in the last 6 months, because the alternator was wired up backwards, putting out 14.65+ the instant the engine cranks over.

Hope they weren't damaged....
Today's start says they are okay, all 8 cylinders fired as they should, and idle was smooth.