My battery is experiencing a parasitic drain from an unknown source...

EDIT: Resetting fuse ECU-B NO.3 fixed the problem.

Hi guys,

I've been troubleshooting this all day and its driving me crazy... Earlier I posted about battery problems and @Spacecoast came back with this advice, "You have a parasitic drain....like a glove box light being on. Use a meter is check for electrical draw (use the DC Amps setting). Disconnect the negative terminal and put the meter between the battery and cable. Make sure the vehicle door is closed and key off. Set your meter to 10DC Amps first. Normal draw is like 1/1000 of an amp."

Sure enough, I did the test and something is draining my battery. I thought I'd be able to locate the problem by disconnect each fuse, then testing to see if the battery is still draining. However after testing each fuse in the relay box under the hood nothing changed. I haven't fully tested the fuse box under the wheel.

The only pin that makes a difference is removing the Short Pin, but that's not a fuse. Does removing the Short Pin indicate a problem with only the fuse box under the hood?

 

Short pin is used to disable a large number of accessories to limit draw during shipping and dealer lot storage.

Spec is 0.040-0.070A

 

I think you mentioned you were measuring A, but I think you need to be measuring V. Keep in mind, if u start pulling interior fuses, you may need to bypass the door switches. “Opening” a door could cause a module to wake up and you’ll be chasing your tail on a false “draw”

 

Ah crap, yeah I was measuring A, not V.

How I was testing the interior fuses was pulling fuse, closing the door, then testing. Bypassing the switch is a much better idea, I'll get some tape and tape the door sensor down.

Time to do some more testing. Thanks!

 

Parasitic drain...sounds like my ex wife

 

There may be a time out as well, 30s, 10m, 1hr etc. same with hood pin switch etc. you can measure, come back in 5m,10m etc. if it doesn’t change after a bit you can be sure it’s not a module firing up. Also, measuring across each fuse is helpful too. Points you directly to a circuit if you find the culprit.

 

First of all, you measure DC amps....not volts...you are measuring current flow. Volts is not power consumption...amps are. Second, every time you make a connection to the battery you "wake up" the vehicle....it may take a few seconds for the vehicle to go back into sleep mode, so you have to keep the reading on for a few seconds. Also, with the hood up you may be already causing current flow since most new vehicles have a hood up sensor and dash warning light.
You need a helper to pull fuses as you take readings. Watch some Youtube videos on how to do this.

 

Measure what across each fuse? All readings across a fuse should be zero unless fuse is open(burned out).

 

Bad advice.

 

How come?

 

Voltage drop.

 

Yeah, didn't make sense to me.

 

All reading are taken by using the meter from a battery terminal to the wire harness that connects to that battery terminal. You are measuring current flow from the battery to the vehicle....in amps. Most meters can not handle much current, so it's critical that everything on the vehicle be off. You remove fuses until you find the fuse that removes the current flow (meter reading). That then identifies the problem circuit, which then give you an idea what to examine.

https://www.youtube.com/results?search_query=how+to+find+a+parasitic+battery+drain

 

Voltage drop across zero ohms? Why would that happen?

 

Where did you get zero ohms from? That’s exactly how fuses work, resistance. Higher resistance, quicker the fuse “pops”.

here’s an actually really good write up.

https://us.autologic.com/news/testing-parasitic-draw-via-fuse-voltage-drop

 

Draw is current, if you use voltage you'll either measure voltage drop (load, which is 12v), or voltage potential (no load, which is also 12v). Very confusing and makes it way harder.

You use current to diagnose draw.

 

https://youtu.be/nELwmfAOz_I


Here some fuse info too.

 

Wrong. A good fuse is a dead short(0 ohms). When you exceed the rated current it blows and opens up(resistance goes to infinity).

 

Tbf. I’m sure I’m getting some terminology wrong.

 

That is irrelevant.