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'02 7.3L Excursion 3.73 Warn Hubs AutoTranny
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Discussion Starter · #1 ·
My truck when I bought it, had a draw down current of 1.1 Amps and left alone for a week, the batteries are stone cold dead.

I discovered this right after I bought it July 5th 2022.
drove to my sister's home, parked it and helped her on the horse ranch.

a few days later, I wanted to drive the truck, and no click, no WTS, no nothing.
Battery was at 3.9 volts.

I sent in the cluster panel to get it fixed.
That dropped the parasitic draw down to 0.6 amps.

better, but not good.

I have a White Rodgers relay sitting idle.
so, I am going to install the White Rodgers relay in series with the +12 volt lead to the electrical system, and route a pair of wires from it to a Dash Switch

Flip switch OFF, no Parasitic Draw.
Flip the switch ON, and start up and drive off.

My airplane had a Master Switch, why not my truck?

Hide the Switch under the Dash, just like I did with my Austin Healy Sprite back in 1964.
Theft Proof ;)
 
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My truck when I bought it, had a draw down current of 1.1 Amps and left alone for a week, the batteries are stone cold dead.

I discovered this right after I bought it July 5th 2022.
drove to my sister's home, parked it and helped her on the horse ranch.

a few days later, I wanted to drive the truck, and no click, no WTS, no nothing.
Battery was at 3.9 volts.

I sent in the cluster panel to get it fixed.
That dropped the parasitic draw down to 0.6 amps.

better, but not good.

I have a White Rodgers relay sitting idle.
so, I am going to install the White Rodgers relay in series with the +12 volt lead to the electrical system, and route a pair of wires from it to a Dash Switch

Flip switch OFF, no Parasitic Draw.
Flip the switch ON, and start up and drive off.

My airplane had a Master Switch, why not my truck?

Hide the Switch under the Dash, just like I did with my Austin Healy Sprite back in 1964.
Theft Proof ;)
I like the general idea. Just one question, will the electric door locks be disabled and the radio clock need to be reset everytime the switch is cycled?
 

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You should actually fix the parasitic draw instead of putting a band-aid on it, IMO. Although a battery cutout isn't a bad idea for prolonged storage.
Your battery draw with the modules asleep should be 50mA or less or 0.05 amps.
 

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'02 7.3L Excursion 3.73 Warn Hubs AutoTranny
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Discussion Starter · #5 ·
the OEM radio is gone,
it was replaced by a former owner with a Flat Screen, and I never refer to the clock on radios anyway.
my cellphone or the GPS on the dash has the Current time.

the Door Lock Panel will be disabled, that is the down side.

I would prefer to fix the Parasitic Draw.... and I thought that it had been, when the instrument cluster panel was repaired, it dropped to 0.004 Amps or 4 milliAmps

I was a bit miffed when I put my brand new Clamp On ammeter on the truck after it had been sitting for almost a week w/o the Battery Tender....
I noticed that the battery voltage was down to 12.3 when it should have been 12.6

the Dash has a LED Digital voltmeter that is 'ON' all the time, I need to see how much current draw that thing has.

I am retired, and I rarely start my trucks anymore.... that is a problem.
The Suburban has a very low Parasitic Draw, have not measured it, but it sits w/o being started for a month or more w/o any problems.

When I take long trips, the Switch would just remain on, so the door lock code panel would work.... make it easy to get back in the truck at a Motel, can't tell you how many times I have locked the keys inside my trucks... that is why I carry a Spare Key in the Watch Pocket of my Jeans.

The truck's Key Fob was not with the truck when I bought it, bought one at a Truck Stop, and it won't program.
 

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How about a battery tender? Easy to install a small one in the engine compartment for those long storage times
 

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John, using the ammeter, and the truck asleep, have you tried pulling fuses to see if you can isolate the circuit(s) causing the excessive draw? If I read your post correctly it looked like you got the draw down to 4Ma at one point but is now back up to .5 (half an amp)?
 
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Discussion Starter · #8 ·
I went through the Fuse Pulling exercise when first looking for the 1.1 Amp draw.
none of the fuses effected it at all. that was back in August 2022

What I do NOT know, is the "Actual Parasitic Draw" right now, when measured with my DVM in series with the Ground Lead the same way I tested it after the cluster panel repair and it was down to 4 milli-Amps

I had a "new toy" in my hands, the Clamp On Ammeter, one that is touted to be extremely accurate, and I wanted to see how it compared to what I saw immediately after getting the gauge panel repaired.

When it warms up enough, the DVM will be put in Series with the Ground Lead, and the Clamp on Ammeter measuring that at the Same Time.... Eliminate the Unknowns.

as for the Battery Tender, I have my big battery charger on it now, in Automatic Mode, it keeps it at 13.3 volts floating. I have a 2.0 Amp Battery Tender brand somewhere in the shop, but the Wx is too cold for me to go digging around for it.


I need to disconnect the Digital VM and see if it is part of the problem, it should be drawing no more than 15 milliamps, but?? I might be disappointed there. If so, it will be replaced. It is tied direct to the Battery.
 
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Sounds like you’ve went over everything John, did you by any chance disconnect your alternator from the batteries when checking for drains?
 

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Discussion Starter · #10 ·
Sounds like you’ve went over everything John, did you by any chance disconnect your alternator from the batteries when checking for drains?
the first time I was searching, yes I did.

this last time a couple days ago, no.

it is a brand new MechMan,
but "what the hey", might as well.

new, ain't always "perfect"
 

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Discussion Starter · #11 ·
temps hit 66 today, so I removed the Battery Tender and took some pictures.

Cable from Bat-1 to Alternator - 0.5 Amps

Automotive tire Hood Motor vehicle Vehicle Automotive design



This needs to be Subtracted from the previous Draw amount, and it indicates that the Alternator itself is drawing 0.35 amps. huh?

Alternator Hot Post to Vehicle Harness ( I don't know what this feeds yet )
That is 150 mAmps draw to the Vehicle, that is at least 100 mA too much.

Hood Motor vehicle Automotive tire Gas Automotive fuel system




this is Bat-2, or Passenger Side, there is a small wire going to the Vehicle harness drawing 0.06 amps or 60 mAmps ( don't know what that means yet either )

Automotive tire Automotive lighting Measuring instrument Gas Vehicle




This is the connections from the vehicle harness, which I "assume" is the PCM?

Wood Automotive tire Gas Electrical wiring Wire



You add 60+150 = 210 mA Parasitic draw by the truck.
that means I have to keep looking, something has changed.
when I first received the repaired Gauge Panel back, Parasitic draw was 4 mA using my DVM in Series with the Battery negative lead.

I have not yet, done an In Series current draw test like I did a couple weeks ago, with a DVM. I need to do that so I can compare Apples to Apples.


I wrote a letter to MechMan and included all of the pictures, and asked them for more Info on what the Terminals are on the connector to the Alternator. emailed that off a couple hours ago.

FWIW,
I just watched a video that compared my Clamp On ammeter, to 6 other brands, one of which is a Fluke..... mine and the Fluke were within 2 mA of each other at about 10 Amps IIRC.
 
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Discussion Starter · #12 ·
An interesting note for those who have not upgraded their Battery Cables.

the following picture is from the PDF from MechMan, I bought a 300 Amp fuse and matching fuse block for the Alternator.


Rectangle Font Parallel Pattern Number



The PDF for my Alternator:
 

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That doesn't look like the stock wiring on my '99. I don't think the '02 main feeds are much different. There isn't anything on the large lug on the alternator except the cable to the battery positive post. The main distribution connection is on the passenger side where the starter relay lives, with fusible links there feeding the main fuse box. Maybe you've got a lot of aftermarket wiring, which will make it a lot harder to track down. It sure looks like a lot of splicing has been done.
 

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Discussion Starter · #14 ·
It used to be a Fire Department Vehicle.

I have found a lot of stuff that needs to be cut out.
 

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Discussion Starter · #15 ·
Last night, I unplugged the Digital VM in the Power Port.
Left a Battery Tender on it overnight, currently showing 12.86 VDC

The draw on the wire from the Alt Big Stud to the truck harness has dropped to Zero mA.

the draw on the Passenger side battery is still at 55-60 mA

the Alternator itself is still drawing too much idle current, Key Off.


Truck Harness wire, draw from alt Stud post.

Tire Bicycle tire Wheel Automotive tire Leg



Draw from Passenger side battery to truck Harness, what is that wire going to?
fluctuates from 55-60 mA

Automotive tire Motor vehicle Automotive fuel system Hood Automotive design



the Alternator Parasitic Draw, Key off is 490 mA today, at 12.83 VDC
Still no reply from MechMan as to why it is drawing current, key off.

Automotive tire Light Motor vehicle Automotive design Red



Bottom Line?
I cannot leave this truck parked long term, without using a Battery Tender.
Very Frustrating.

If I can't get this resolved, I am going to use a White Rogers high Amperage Relay to disconnect the Alternator, Key Off.

.
 
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Discussion Starter · #16 ·
at 4 pm today, Tuesday.
I lifted the heavy cable from the Alternator off of the Battery + terminal.


at 10:30 tonight, I go back out with more diagnosing thoughts....
Betcha that Alternator is being told to do something by the truck's ECM...

uh, huh, it sure is. there is 4 mA draw to the Alternator on the Orange Wire, even though the Alternator is not hooked up to the battery.

Now, I need to hit the Schematics book that I bought last month and see "WTH" is going on?

The Passenger side Battery wire to the truck harness is stable, at 60mA like it has always been.


I left a small 800 mA Battery Tender on it, it has brought the Batteries up from 12.81 at 4:30 pm to 13.1 now at 10:30 pm, and by tmw, I am willing to bet it will be at 13.3 floating voltage... just like it does with my motorcycle.
 

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I may be wrong but if I remember right the only trucks that the PCM has anything to do with the alternator are on those with dual alternators and it only controls the second or lower alternator

Sent from my SM-A426U using Tapatalk
 

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Discussion Starter · #18 ·
I don't know how this truck left the Factory.
When I bought it, it had a Humongous Leece Nevelle alternator on it, with 3 wires going from the truck harness to the alternator.

there isn't any brackets, or room on the Passenger side for a 2nd alternator.
 

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The cluster repair must still be doing something since leak current has dropped from the common (among those of us afflicted with it) 1.1 A to 0.5 A.

The red flag is the (reverse) current going into the alternator via it's output lug (key off engine off). Inside are diodes with extremely low reverse-bias current ratings. These are not gated components that might be influenced by other inputs. They should be blocking the leak in every state and under all conditions.

In parallel with the diodes is a capacitor designed to limit ripple. If it were the culprit, there would be a much higher AC component in the DC charge current (engine on). Too many years since alternator bench work, can't remember the numbers, but don't think it could be this as leak current would be higher.

So my targets are now the small relay inside the cluster and one or more diodes in the voltage regulator pack. Soon as it warms up a little, I'm on it. Thanks for sharing.
 

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Discussion Starter · #20 ·
Bob7.3
You missed that the Alternator Positive Post is where nearly all of the parasitic draw is now, it is the Culprit for the high parasitic draw... I wrote MechMan an email about this, they have NOT answered me yet.

I lifted that cable off of the Driver side battery 2 days ago, now there is a small 2 mA draw thru the Orange Wire to the Alternator regulator plug.

Plus there is a 50-60 mA draw from the Passenger side Battery to the truck's wiring harness.
That is what is keeping the PCM and gauge cluster powered up. With this cable connected, the Key Pad will lock/unlock the doors. ( this draw is 50 mA to 60 MA, depending on Battery Voltage - a normal condition )

with it lifted off, the truck is DEAD.
 
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