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Discussion Starter #1
Hi,
I looked through the “secrets”, found another person with the same issue, but the thread ends with no resolution.
E-350, 2000 7.3, dual alternators.
Brand new Autozone Duralast gold go dead in a day or two.
Alternator(s) putting our 14 volts at 1500RPM
Alternators(s) putting 45 amps into partially charged batteries @ 1500 RPM

Power off, connect amp meter between that big connector where both batteries + connect and the under hood battery +, get 4 amps of current.
This is with all the fuses and relays pulled out of the fuse box near the brake booster.

Factory manual says current should be no more than 50 miliamps.

I read the factory manual procedure about connecting a jumper so as to avoid powering down the van
electrical, as things will react to loss of electrical power and make the testing amp readings invalid.
Have not exactly figured out how to do this with two batteries at the same time.

Planning to completely disconnect the frame battery for testing, just use the under hood battery while testing.

So the batteries and charging system are working fine, but something is not disconnecting when the ignition key is turned off, and killing the batteries.
Any advice appreciated!
Frank
 

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Just disconnect one of the batteries.

Sent from my SAMSUNG-SM-G935A using Tapatalk
 

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Brand new Autozone...
There's your FIRST problem...
...4 amps of current.
This is with all the fuses and relays pulled out of the fuse box near the brake booster.
Well, it certainly appears that there's excessive parasitic drain. But you haven't told us much detail about how you did the test, or what's on the truck. Does the truck have RKE, or any aftermarket electronics? Was the alternator warm? When did this symptom appear? Did something happen to the truck just before? Why & when did you replace the batteries? Click this, read the caption, and follow its suggestions about your profile & signature:

Factory manual says current should be no more than 50 miliamps.
That's the UPPER limit, and it's just a universal rule-of-thumb. The lower the parasitic loss, the longer you can go between charging the battery (batteries), as with the alternator by driving. But the exact amount of time depends on a LOT of factors, including the number of batteries, their ACTUAL Ah capacities, how much current the starter needs to spin the engine (higher for high-compression engines, like diesels), how much current the OTHER engine management systems need (ignition & EFI on a gasser; glow plugs, etc., on a diesel), the battery temperature during cranking...

The point being: 50mA is a good general upper limit, but the TYPICAL draw is closer to 15mA (for PCM KAM, clock, radio presets, RKE...).
 

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The way to connect an ammeter for testing is to open the door for access and wait till the modules go to sleep.
Then disconnect one of the battery leads and connect your ammeter inline. THEN disconnect the second battery.

Doing it that way prevents the modules from going "live" and doing things like turning on the dome light, which would probably blow the fuse on your ammeter (you need to use the low range, which is probably limited to 2 amps or so.)
 

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Discussion Starter #5 (Edited)
“Open the door” is one of the problems.
I took all the fuses and relays out of the fusebox next to the brake booster. (still had over 4A of current from the batteries)
Today, I found that there is a second fuse box next to the brake pedal also needs to be accessed for testing.
No way to access it w/o opening the door.
Opening the door turns on the dome lights, etc. Game over.

There must be a switch or sensor that detects the open door.
i’ll try to locate and defeat switch so I can have the door open to access the smaller fuse box next to the brake pedal.

The manual says to drive the van for about 20 minutes before doing the test.
I made the temporary ground jumper today, so I can follow the procedure to insert the ammeter w/o opening the circuit.
Hope to do that tomorrow.

The manual also says that if excess current is still flowing after pulling all the fuses & relays, it is the “generator’
Top alternator was installed at 147,000, so it has 113,000 on it.
Voltage and charging current are fine, but there could still be an electrical issue in either alternator causing the current draw.

Might just disconnect the B+ on the back of each alternator and see if that effects current draw.
Also, looking at the schematic, seems like the starter solenoid relay always has B+ on it, might disconnect that too and see what happens.

I took the van off the road in 2014, did not need it until now.
Batteries seem to last about 2 to 3 years, the old batteries would not hold a
charge, so AutoZone gave me two new ones free, as the old batteries were within the adjustment period.

Here is the build sheet, nothing special about the van.


The only modifications not shown on the build sheet are:
Installed a HD4R100 transmission @ 203k miles, as the old transmission was kaput.
Installed a DAHL model 100 fuel filter/water separator in the fuel line.

Frank
 

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If you leave the door open, the interior light should normally turn off after a bit, indicating that the PCM and other modules have "gone to sleep".

You can check the alternator B+ connections by removing the nut then in the dark disconnecting the terminal watching for a spark as it breaks the connection. If you do see one, that indicates that the diodes in the alternator are done for.
 

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Discussion Starter #7
Progress!
Disconnecting the B+ on the top alternator , current draw drops from 4A to .1A (one tenth).
And this is w/o following the regime to quiesce all the active electronics, so I'm replacing that guy!
 

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Discussion Starter #8
After an hour or so, it settled down to 123 ma.
I realize this is more than the manual says (55 ma), but it is not 4 amps, so I’ll take it.
A current draw of 123ma is not going to weaken the batteries overnight, so the van won’t start in the morning.

Wanted to disconnect the B+ on the lower alternator to see if some of the current leakage was coming from there.
However, after getting under the van, it appears that the lower alternator is not accessible at all.

I remember that to change the lower alternator, I had to take out the radiator & all related stuff to get to it.
HELL NO

So I’m done until the replacement upper alternator arrives. Ordered a new one (no core) from Rock Auto.
Test setup:
Disconnected the frame battery, so only the top battery was used for testing.
Connected milliamp meter between top battery + terminal and top battery + cable.
Connected wire between top battery + terminal and top battery + cable.
This way, I can cause the current to flow through the wire or the meter, or both.
The idea is that the battery is never disconnected from the van electronics, which stay powered up, sleep-mode, at all times.
Waited an hour for sleep-mode, then took measurements.



 
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