Parasitic battery drain

[Tim C]

Hi All,

Hoping to get some direction on diagnosing a battery drain issue I'm having.

For reference, the reading directly between the positive and negative lead is 12.27
I've disconnected the negative lead and hooked a multimeter up between the negative lead and the negative post. I've disconnected the hood light.
Reading starts and stays as 12.18 amps.
I've pulled all the fuses from the fuse panel in the engine compartment (as far as I can see, there is no fuse panel in the passenger compartment.) No changes in the reading.

I did notice that if I open then close the door hard, the reading drops to around 11.68 then slowly climbs back up to 12.18. If I close the door lightly, there is no drop.

Given this, I'm thinking there is a short somewhere (shaking of the truck by closing the door momentarily breaks the short).

Given all this, any suggestions on how I continue to investigate the cause of the drain?

Thanks in advance!

 

[KC Cryptkeeper]

I'm guessing the truck is not running? 12.18 without running still seems on the low end. what is the reading with the battery disconnected? What is the reading while the truck is running? You need to establish a good baseline for several different situations so we understand why are what is causing the VD.

 

[Jimmy07]

I'm guessing the truck is not running? 12.18 without running still seems on the low end. what is the reading with the battery disconnected? What is the reading while the truck is running? You need to establish a good baseline for several different situations so we understand why are what is causing the VD.

He’s doing an amp draw test, not voltage drop. 12.18 is the current being drawn with the truck off.
@Tim C, that is EXTREMELY high for the truck being off (like equivalent to both headlights being on). There is one other fuse outside the fuse box, and that is the radio fuse which is by the battery near the brake fluid reservoir. There’s one other item not associated with the fuse box I can think of, and that’s the alternator. Was your initial test pulling one fuse, putting it back, then the next? How about pulling them one at a time and leaving them out?

 

[KC Cryptkeeper]

He’s doing an amp draw test, not voltage drop. 12.18 is the current being drawn with the truck off.
@Tim C, that is EXTREMELY high for the truck being off (like equivalent to both headlights being on). There is one other fuse outside the fuse box, and that is the radio fuse which is by the battery near the brake fluid reservoir. There’s one other item not associated with the fuse box I can think of, and that’s the alternator. Was your initial test pulling one fuse, putting it back, then the next? How about pulling them one at a time and leaving them out?

You don't do an Amp draw across terminals, you use a CT around the positive cable. He is talking about voltage drop as without the truck running and the power being used the battery's voltage is going down resulting in a dead battery.

 

[Jimmy07]

I've disconnected the negative lead and hooked a multimeter up between the negative lead and the negative post. I've disconnected the hood light.
Reading starts and stays as 12.18 amps.

You don't do an Amp draw across terminals, you use a CT around the positive cable. He is talking about voltage drop as without the truck running and the power being used the battery's voltage is going down resulting in a dead battery.

What he described doing in the quote above is an amp draw test (parasitic drain).

 

[KC Cryptkeeper]

What he described doing in the quote above is an amp draw test (parasitic drain).

Again you CANNOT test amp draw that way.

 

[Jimmy07]

https://testmeterpro.com/parasitic-draw-test-with-a-multimeter/

 

[KC Cryptkeeper]

https://testmeterpro.com/parasitic-draw-test-with-a-multimeter/

For reference, the reading directly between the positive and negative lead is 12.27

Still not what he said. He is reading voltage period.

 

[KC Cryptkeeper]

Why copy and paste when you can go to your toolbox and get what you need? The one on the far left is with me all the time.

 

[Jimmy07]

Again you CANNOT test amp draw that way.

Still not what he said. He is reading voltage period.

Unless the electrical laws have changed....

I've disconnected the negative lead

!

maybe he didn’t do this?

and hooked a multimeter up between the negative lead and the negative post.

maybe he actually missed this step?

Reading starts and stays as 12.18 amps.

maybe he mistyped amps, and it’s supposed to say volts? Maybe he forgot to switch over to the amps setting (in which case, no reading at all)?


I’m well aware of what an inductive ammeter is and the fact that you can perform a parasitic draw test using one, in addition to the procedure he outlined above. I’ll stand corrected if you can explain to me how the exact steps that he described is NOT an amp draw test.

 

[KC Cryptkeeper]

Unless the electrical laws have changed....maybe he didn’t do this?

maybe he actually missed this step?

maybe he mistyped amps, and it’s supposed to say volts? Maybe he forgot to switch over to the amps setting (in which case, no reading at all)?


I’m well aware of what an inductive ammeter is and the fact that you can perform a parasitic draw test using one, in addition to the procedure he outlined above. I’ll stand corrected if you can explain to me how the exact steps that he described is NOT an amp draw test.

If he is getting anything over 50ma draw with the battery disconnected he has major problems, a draw of 12 amps would have to be something in line with a motor. Other than the fan blower motor I can't think of anything that would create that much draw. Even dead shorted I can't see that much current draw.

He started with a voltage reading of close to the same number as his amp draw which lead me to believe he was always giving us the VD.

 

[chrisbh17]

If he is getting anything over 50ma draw with the battery disconnected he has major problems, a draw of 12 amps would have to be something in line with a motor. Other than the fan blower motor I can't think of anything that would create that much draw. Even dead shorted I can't see that much current draw.

He started with a voltage reading of close to the same number as his amp draw which lead me to believe he was always giving us the VD.

Forever ago a friend of mine was hunting a large parasitic draw on his wife's Mercedes. Turned out to be the power seat of all things....that can draw 12A I bet!

 

[Jimmy07]

If he is getting anything over 50ma draw with the battery disconnected he has major problems, a draw of 12 amps would have to be something in line with a motor. Other than the fan blower motor I can't think of anything that would create that much draw. Even dead shorted I can't see that much current draw.

He started with a voltage reading of close to the same number as his amp draw which lead me to believe he was always giving us the VD.

I agree. That’s why I also mentioned it’s an extremely high number. I also had to re-read his post a few times to differentiate if he was referring to voltage compared to his initial, but every step he’s taken points to current draw (assuming...). Hopefully he’ll chime in, double check, and clarify.

 

[KC Cryptkeeper]

Forever ago a friend of mine was hunting a large parasitic draw on his wife's Mercedes. Turned out to be the power seat of all things....that can draw 12A I bet!

True still a motor, in fact I didn't think of that one.

 

[chrisbh17]

True still a motor, in fact I didn't think of that one.

If the draw is really 12A, pretty much anything on a circuit greater than 10A can be the culprit and there are quite a few of those.

Seat heaters, HVAC (blower motor and/or resistor, vent deflector motors, etc), power mirrors, power windows, electric steering, BCM, PCM, TCM, ABS, trailer wiring, power outlets, inverter, radio amp, door modules, air suspension, adjustable pedals, sunroof

So, yeah, it can be a LOT of stuff! And thats just the big circuits, it could also be a combination of smaller ones too.

Basically a PITA no matter how you measure it.

 

[KC Cryptkeeper]

If the draw is really 12A, pretty much anything on a circuit greater than 10A can be the culprit and there are quite a few of those.

Seat heaters, HVAC (blower motor and/or resistor, vent deflector motors, etc), power mirrors, power windows, electric steering, BCM, PCM, TCM, ABS, trailer wiring, power outlets, inverter, radio amp, door modules, air suspension, adjustable pedals, sunroof

So, yeah, it can be a LOT of stuff! And thats just the big circuits, it could also be a combination of smaller ones too.

Basically a PITA no matter how you measure it.

You realize over half the stuff you mentioned is a motor driven piece, even heating elements in the seat are rated the same as a motor when calculating load.

 

[chrisbh17]

You realize over half the stuff you mentioned is a motor driven piece, even heating elements in the seat are rated the same as a motor when calculating load.

I never said they werent just that there are many circuits capable of shorting out to 12A draw. And only half of them are motors

 

[RoadRamblerNJ]

Most "multi-meters" have a 10 Amp max limit. He said nothing about using a clamp meter so, I also think he's measuring a voltage drop. That said, the reading suggests the battery could be on it's way out.
It would be great if the OP could chime in here and provide more info. Also, how long does this take to kill the battery? Hours? Days? Weeks?