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Discussion Starter · #1 ·
I have a 2001 7.3 . Battery voltage is reading 25.2 v, is it supposed to be reading that high from hooking up to one battery? I’m asking because the truck has been having glow plug problems. Has code p1106 ( dual alternator lower fault) and p0381 glow plug code. Has brand new glow plugs and harness. Also ses light is on
 

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25.2 volts??? You should only have 12.4 or so volts. If you have hooked the batteries in series (higher voltage) rather than in parallel (more current) then I would expect that everything electrical is toast on your truck.

Cj
 

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agreed. 25.2 volts sounds like batteries are hooked up in series, not parallel.
engine off battery voltage should be roughly between 12.3 and 12.8 volts
 

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Yep, definitely sounds like batteries are connected in series
 

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Is that voltage with the engine running or when it is off?

If running then the voltage regulator is shot on the alternator.
 

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Discussion Starter · #6 ·
That’s with the batteries off. I also tried to unhook one battery and the reading is still 25-26v. Any way to hook the batteries up properly ?
 

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Your batteries should be connected positive to positive with both negatives going to block grounds.

The only way that I can see that this might happen is if someone made up some new cables or bought some cables from a parts store and connected them wrong. How long have you had the truck and did someone else try to fix it?
 

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Discussion Starter · #9 ·
I’ve had it for like 6 months. And no I don’t think so. I’ll check it out . Never thought to look at the cables or what kind of setup they have
 

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A stock set of cables will have:

Drivers side positive a single cable going to the passenger side where 2 cables will be under the same lug on the positive. Now on my 96 it will then split into 2 wires, a heavy gauge one and a smaller gauge one. The heavy gauge wire goes to the starter and the smaller gauge wire go to a fender mounted relay. Yours may be slightly different.

The drivers side negative should go down to a block ground on the front drivers side of the block.

The passengers side negative should go down to a block ground on the front passenger side of the block

You might also want to disconnect at least one battery the next time that you test them.
 
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Discussion Starter · #11 ·
So it appears that there is a heavy gauge black wire coming from the positive terminal down to the starter. Then a red going to the starter relay, then the other red to the other battery. Then there is a black from the negative terminal down to the lower alternator, and a small black wire grounded to the fender. No ground to the block . The other side I believe it grounded to the block . And the red from the passenger side battery. What needs to change?
 

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Where are the wires going from the positive + and negative - sides of the batteries. From what you are saying the colors are not right. You may have to crawl under your truck to figure it out.

Stock it was drivers side battery red cable to the positive post + to the passenger side battery positive post + red cable to the starter and red wire to the relay. All black wires were to block or body grounds.

Here is a diagram that may come close to what you are working on.

 

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Discussion Starter · #14 ·
So the black wire on the negative side of the batter goes down to the alternator directly. Then a small black wire from the negative side grounds to the inner fender. The one red goes over to the driver side battery , the other red goes to the starter relay on the passenger side. Then a thick black wire connected to the positive terminal goes to the starter . This pic is the passenger side battery of the truck
 

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disconnect the driver side battery. read the voltage on passenger side battery, and on driver side battery. should be around 12.3 to 12.8 volts for each battery.
if that checks out, connect the driver side battery, and disconnect the passenger side. test again.
should be the same 12.3 to 12.8.

then reconnect positive to positive, and negative of each side to a bolt hole on the block.
this should give you 12.3 to 12.8 volts across each battery.
 

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So the black wire on the negative side of the batter goes down to the alternator directly. Then a small black wire from the negative side grounds to the inner fender. The one red goes over to the driver side battery , the other red goes to the starter relay on the passenger side. Then a thick black wire connected to the positive terminal goes to the starter . This pic is the passenger side battery of the truck
Engine off, key off, disconnect all wires from either batteries Postive post (red) use volt and with one one postive battery post, the other on the same battery negative post you should read about 12 volts. If not, throw your voltmeter away and get a new meter.
 

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Discussion Starter · #17 ·
So is the black not supposed to connect directly to the alternator?
disconnect the driver side battery. read the voltage on passenger side battery, and on driver side battery. should be around 12.3 to 12.8 volts for each battery.
if that checks out, connect the driver side battery, and disconnect the passenger side. test again.
should be the same 12.3 to 12.8.

then reconnect positive to positive, and negative of each side to a bolt hole on the block.
this should give you 12.3 to 12.8 volts across each battery.
thanks buddy. But what about the black that goes directly to the lower alternator? Do I add another thick black wire to the block and leave the other black wire on the lower alternator?
 

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What you have is a mess of a modified charging system and it is going to be difficult to figure it out without being there with you.

The schematic that I posted is for a stock dual battery system on your truck. From what you have described and the picture that you posted will have most of us scratching our heads.

But here is what I would do.

Disconnect all the cables from both batteries and check their voltage. You should have close to 13 volts on each battery.

Forget about the battery alternator down low on the drivers side.

Rewire the batteries back to stock that I described in a post above.

Once everything is working properly off of the alternator on the passenger side top, wire in the second alternator according to the schematic that I posted.

Sent from my SM-J737V using Tapatalk



edited by 1970something to fix typo.
 
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Discussion Starter · #19 ·
Okay thanks a lot brother. Also one more question , you said passenger side top, did you mean driver side top alternator? I have an alternator on drivers side top and an alternator underneath on passenger side
 

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Discussion Starter · #20 ·
Also, sorry if I sound dumb, this is my first Powerstroke, but where are those wires going? I know the one on the left (drivers battery) goes to ground in the block, for the right battery where are those 2 negative wires supposed to go?
 
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