Need some help with a direction to go with charging system ?

[1951M1078]

Put in all new battery's and the system when all spazzed out ( flashing reds then amber's then some green then reds then amber's and reds )and then back to RED 14v and no light on the 28v.

Pulled the lines off the revers polarity box and cleaned and reinstalled. SAME.
Put the battery's that had been in it and it tried to work but back to RED at 14v.

Looks like this problem is above my pay grade. For the life of me I can't see why it was made this complicated ? Don't get me wrong that is one smart regulator but come on,really .Its like $700+ new (if you can get one ) and used $300+. And the only way to finishing the testing is with a "known good regulator".

I'm back to the original question .

Go aftermarket ? (and pull most of the stuff between the battery's and the alternator .will need to see if that can even be done)
Go used alternator and regulator ? ( and only God knows how long that will keep working)

If only the light would go on in my head ! Sad.

 

[coachgeo]

Put in all new battery's and the system when all spazzed out ( flashing reds then amber's then some green then reds then amber's and reds )and then back to RED 14v and no light on the 28v.....

review your wiring up of all new batteries. Look at it like... "ok I wired it up wrong...... where is the error"? granted you may have wired it up right.... but going in with that assumption makes it easier to miss a mistake.

 

[1951M1078]

Where do I find the wiring diagrams ?

This is saying I or someone has re wired the truck wrong ?

 

[coachgeo]

supposedly it is on the underside of the battery cover. It is not on mine. there is a thread in here that shows the two different battery connection arrangements.

ahhhhh.... here you go

https://www.steelsoldiers.com/showthread.php?158074-FMTV-Battery-hook-up-diagram

 

[1951M1078]

Thanks.

But that is the way it is wired. (at the battery's )

The one thing that is not on the tag on the battery box is, Their are 2, 28 volt wires (coming from the motor ) and one 14 volt wire and one ground..
I know their is a heavy ground at the starter and a heavy positive. I just figured the other went to the dash ? But now I'm going to go trace it to its end.

 

[1951M1078]

So, what is a M1078 Alternator with regulator worth, not working ?

 

[Suprman]

They are still worth money. Good chance your regulator is good and the alt is not. Since it works for a second or two when you start the truck. Dont get rid of any of it. Peek in with a light see if maybe a piece of something fell into the alt. Take it off and shake it.

 

[1951M1078]

Worth a try. Thanks.

 

[1951M1078]

I go out to the truck to move it and pull the Alt.

And it is working ! Really ?????

I give up.

 

[Suprman]

Something is going on there. There are separate cables going to the starter from the batteries. Then you have 12 and 24 volt cables going into the cab thru the polarity box. And a pair of 12 and 24 volt cables from the alternator to the batts.

 

[1951M1078]

Will, can you point me to a cable diagram ?

The cables off the Atl. go to the polarity box.

I will need to trace the other cables and where they go.

At the batterys, I have two 28v cables ,one 12v cable and one ground cable.

The starter has one heavy ground cable ( at that post their some others, ground wires and one heavy ,flat cable to chassis. and one heavy 28v cable.

 

[Suprman]

The alternator cables go to the same terminals on the polarity box that the battery cables do (in). The cables going to the cab come off the other terminals on the polarity box (out). You have a big 24v batt lead right to the starter and a big ground to the starter from the batt box. All of the grounds branch off from this main ground I believe. You can add an extra ground from the batt box to the frame.

 

[1951M1078]

Its back !!!

Think I will add a ground tomorrow and start looking for ????.

What a machine !

 

[1951M1078]

Found the wiring diagrams.

Do I have this right,truck only uses one 12 volt battery ?

 

[Suprman]

4 batteries. Two 12 volt batteries in series paralleled to another matched series pair. So you have the negative, then between the two series pairs is 12 volt and both series sets make 24 volts.

 

[1951M1078]

That is the way I have on the truck but I was looking at the diagram . Need to look at it again.

Looks like BT3 and BT4 . got it.

 

[1951M1078]

What is the shunt current measurement being used for ? This is a little out of my pay grade.
Is this something that could make a surge ?

I feel something is making the regulator think their is some very big load.
Its like a poor ground or something ! Show yourself !

 

[Suprman]

I think the shunt is used for the diagnostics. The regulation voltage lead cones thru the cab power panel, which goes thru the polarity box. Although the fuel solenoid is a better connection, it’s still from the same source. If you are getting an intermittent drop in voltage at the panel, and the regulator senses it, and tries to bring the voltage up, and then a second later you have an over voltage situation and the alt shuts down. I would bypass the polarity box. You can temporarily run a fused/breaker protected wire from the 24v battery connection over to the regulator 24v connection. Take the lead that’s on there now off and tape it up, at least for now. See how it goes with a direct connection like I have described. You will want to pull the fuse when the truck is off since this connection won’t be disconnected when you shut the truck off. See what happens.

 

[1951M1078]

Think I should go all the way back to the battery for a clean 28v supply ? Its no big deal to do that.

 

[Suprman]

You just cant leave it permanently connected. Needs to be switched with the truck ignition.