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arnoldauto
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Reged: 11/27/03
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Calling all Electrical EXPERTS...draw on battery (.186mA) lets pick some brains
#1504287 - 11/28/03 11:17 AM
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This guy brings this 2000 F350 Super Duty in. Batteries goes dead overnight. The truck has dual alternators. The batteries look original, but when tested with my Snap-On Micro Vat they pass with flying colors. Here's the deal, I can pull the #22 50 A fuse in the battery junction block which kills the draw. That leads me to the fuse's which feed off of that. The #15 5A fuse in the fuse panel, with the #22 plugged back in, will then kill it. That feed the IPC, the wipers, the GEM, transmission selector, brake pedal posistion sensor, and brake fluid level switch. I've disconnected all of these except the wipers. The GEM kills the draw completely. I've gone so far as to pull the individual connectors off the back of the GEM. The top one disconnected leaves .117 mA, the bottom one disconnected(top one reconnected) leaves .080mA. Book specifications for a parasitic drain are .050 mA. I've even pulled individual wires from the GEM connectors, one at a time and plugged them back in. The only one to make a complete difference is the GEM ground. NOW the question, has anyone heard of this? Is a .186mA draw normal? Could the batteries be the culprit? I've heard they only last three years and they are the original Motocrap batteries.  Please help me end my misiries. 
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arnoldauto
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Reged: 11/27/03
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Re: Calling all Electrical EXPERTS...draw on battery (.186mA) lets pick some brains
#1504295 - 11/28/03 11:25 AM
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RSNYDER952 had a similar post. Go to search, and under 7.3L POwestrokes.... type BATTERY DRAIN and search within a year....almost exact, but he never foolowed up, now his email is no good...:(
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BeachCity
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Re: Calling all Electrical EXPERTS...draw on battery (.186mA) lets pick some brains
#1504318 - 11/28/03 11:46 AM
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arnoldauto,
I guess the first thing to do is to welcome you to the site.  You're in the right place. 
As far as the current drain is concerned, I would not be too concerned with anything below 500 milliamps. Parasitic drains from cars and trucks in the 80's and early 90's typically had parasitic current drains of 200 to 400 milliamps without any problems. Circuit design today is better, and the current draws have gone down. Even half an amp shouldn't pull down one (much less two) battery(s) overnight.
Sounds to me like one of the batteries has a shorted plate, and is pulling down both batteries overnight. I used to have a Bear "ARBST", and it would sometimes catch these. Have not seen a SnapOn "Mini VAT", but even a full sized VAT usually won't catch a battery that has shorted plates. I would disconnect the batteries, leave it overnight, (or whatever it takes to normally cause the discharge) and retest in the morning. Bet you'll find one dead.
Let us know, so that when the next person that has this problem does a search, they won't come up "empty handed" like you did.
Erick
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arnoldauto
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Re: Calling all Electrical EXPERTS...draw on battery (.186mA) lets pick some brains
#1504324 - 11/28/03 11:52 AM
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Thats where I am headed. My shop is 30 miles from here. I figure I can go in and charge them up on the way, disconnect and retest tomrrow. I will definitely follow up and thanks for the reply.
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Maroon Harpoon
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Re: Calling all Electrical EXPERTS...draw on battery (.186mA) lets pick some brains
#1504328 - 11/28/03 11:54 AM
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Bummer!
Are you checking the GEM (general electronic module) with the doors shut? At any rate, it wouldn't be the batteries...it would be the drain and it sounds like you have it narrowed down...have to see what the GEM is controlling that won't shut off. May be a relay stuck. Its gonna be fun...wish I could be more help.
Welcome to the Diesel Stop!
MH
Tim
After reconsideration, I have to agree with Eric! Tim
Edited by Maroon Harpoon (11/28/03 11:55 AM)
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arnoldauto
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I've been to several sites...the max parasitic drain should be .050mA???HELP!!
#1504451 - 11/28/03 01:45 PM
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the ASA website said .050mA, and a couple others...Can anyone help me here, I'm begging now...if someone has a duplicate vehicle, would they mind checking their draw..??? thanks again guys..
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444-4D
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Re: I've been to several sites...the max parasitic drain should be .050mA???HELP!!
#1504550 - 11/28/03 03:11 PM
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I'm going to tell you how to check a vehicle for a draw. I know you all are wanting a lesson  . Remember I haven't worked on a vehicle in several years. The modern electronics may prevent this from working but I don,t think so.
1. Use a volt meter not an amp meter.
2. Disconnect both + battery cables,leave the - side connected.
3. Make sure everything is turned off, doors shut, etc. and don't forget to disconnect the hood light. You are going to use it as one of your tools.
4. Connect the - voltmeter lead to the - bat post and the + voltmeter lead to the + battery post. Remember the voltage. You are just checking the battery voltage nothing else.
5. Connect the - voltmeter lead to the + battery post and connect the + voltmeter lead to the end of the disconnected + battery cable. If the voltage reading is less than the battery voltage you do not have a drain.
Now back to the hoodlight. If the voltage is less than battery you can touch the hoodlight wires together and watch the voltmeter to comfirm a draw or no draw.
One other thing. If the voltage reading is the same as battery voltage, momontarily touch the + cable to the + post and see if the reading changes.
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arnoldauto
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ACTUALLY, the most accurate way to check for a draw is using amps.....read inside
#1504626 - 11/28/03 04:32 PM
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MOst experts agree. The old way was using volts, however this was not accurate enough. Amperage is actually like the speed, instead of the highway(voltage). If that is even a picture at all..lol. When I said my vehicle had a draw, I tested this by putting my Mac tools multimeter in series with the circuit(battery -). I disconnected the negative cables on both batteries, leaving the (+) connected, then taking one negative cable and clipping it to my negative lead on my voltmeter. The positive lead clipped to the battery post. With doors shut(they will draw 3.3+ amps with interior lights on), I then plug my leads into the meter, and quickly turn it to the 10A scale. The draw would read .186 A or 1.86 mA(milliamps)Voltage would read however, battery voltage, as that milliamps is not enough(unless given enough time) to draw voltage down. So, in essence amperage testing for a draw is more instantaneous.
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444-4D
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Re: ACTUALLY, the most accurate way to check for a draw is using amps.....read inside
#1504657 - 11/28/03 05:03 PM
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I guess I must be a real dinosaur. Racing with DC current makes no sense to me. 
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LarryM
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Re: ACTUALLY, the most accurate way to check for a draw is using amps.....read inside
#1504726 - 11/28/03 06:03 PM
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Quote:
The draw would read .186 A or 1.86 mA(milliamps)
A nit pick and I'm sure it was probably an oversight, but just so you're converting things right .186A is 186mA not 1.86mA.
Also, I really don't know how to check this, but I do agree that what Erick suggested is a good start since a bad battery will kill the whole shabang very quickly. Using voltages might be tricky with a dual parallel battery system.
Good Luck sometimes this electrical stuff can be a real "snipe" hunt 
Larry
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arnoldauto
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Using a Fluke meter or like, if on the mA scale, the reading was 1.86 mA....honestly..
#1504743 - 11/28/03 06:20 PM
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and on the 10A scale it reads .186 A.
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Preparation_H
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Re: ACTUALLY, the most accurate way to check for a draw is using amps.....read inside
#1504758 - 11/28/03 06:38 PM
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Disclaimer: I'm no electrical expert 
New school :
Do not disconnect the batteries , this may activate relays that you may not want to, and create a electrical draw and fool you into chasing your tail .
Use a low amp inductive (current) probe to check the system with everything connected.
Erik covered the rest .
Anything under 500ma is cool in most cases.
Correction 50ma
Keep in mind that in today’s vehicles there are many relays that will not shut down for as long as 45min to a hour after the vehicle has been shut down. So it is not uncommon to see well above 500ma
Correction 50ma
current draw for some time after your steed has been shut down.
From back here in the cheap seats I’ll take a SWAG and go with the batteries. Check them first by specific gravity and the load test them disconnected separately. 
Happy Hunting
Edited by Roadagent (11/28/03 09:32 PM)
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Iluvsteelies
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Re: ACTUALLY, the most accurate way to check for a draw is using amps.....read inside
#1504873 - 11/28/03 08:26 PM
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500 miliamps is a lot.
Way to much.
You will generally see a max of about 50 miliamps as a rule of thumb.
You are more than correct that a lot of new cars have multiplex modules that will draw 150-200 miliamps for about 45 minutes like you said before they "go to sleep".
The best way to check for draw is with ammeter. Probe the battery terminal with the cable still hooked up and aligator clip the other end to the cable, then remove the cable from the terminal. This way you won't lose power and wake things up and you will eliminate the spike caused by capacitors that must charge up if you were to interrupt power.
Arnoldauto, A 185 miliamp draw isn't going to kill two 850 CCA batteries overnight or even make a dent, it would take more like a week.
Me also thinks batteries are bad.....Wait a minute aren't you a tech?
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dzl wannabe
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Re: ACTUALLY, the most accurate way to check for a draw is using amps.....read inside
#1504922 - 11/28/03 09:16 PM
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50ma is normal draw.
Drive vehicle for five minutes, at over 30mph.
Allow vehicle to sit for 40 minutes
Install small jumper to neg. post, remove neg. cable, insert meter, disconnect jumper, not more than 50ma, maybe an 80ma pulse.
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Preparation_H
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Re: ACTUALLY, the most accurate way to check for a draw is using amps.....read inside
#1504938 - 11/28/03 09:29 PM
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Amazing the difference a zero can make
oppps
I stand corrected
Using a volt meter for a parasitic draw 
You can get fooled doing so. Transistor devices will show the
voltage potential but should not draw over a few milliamps current in most cases.
Current is what you are looking for as it represents "work” or lets say the volume of water coming out of a hose.
Voltage indicates the possibility of doing work or like the water pressure coming out of the hose.
FYI
Calculating the maximum allowable parasitic drain for a vehicle is related to the reserve capacity of the battery. If the battery reserve capacity is 100 minutes, than the max parasitic draw is 25% of 100 = 25ma. Keep in mind that this is the MAX and how GM figures it.
Edited by Roadagent (11/28/03 09:45 PM)
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