Diagnosing parasitic drain

Beat me to it. Using P=I^2*R, 10A through a 100 ohm resistor would be burning 10,000 watts. Maybe if the meter was water cooled?

 

Thanks guys! I'll get back to testing that those fuses a little later. I don't believe the fuse is blown just because it beeps at me and says LEAD which the Fluke guy says that means the fuse is good.

I tried back at just getting a current reading with a different new Fluke 87 and 77. I am still not getting any current reading. Can you tell me if these are the right settings? This is through the positive - it is the same with the negative side.



I went ahead I tried just checking each fuse before this while the car has been asleep for an hour. Each read ~.00 mV

I wish I could just check the current through the cable and the battery and do the fuse pull method

 

So your red lead looks wrong. You've got them in the 10A hole, needs to be one to the right to get mA

 

Here is what I get. The same as just reading the air around me

 

Are the connections to those terminals nice and clean?

 

I'd say so. I can maybe clean the cable a little more. The strange thing is when I clamp the alligator clamps between the battery and the cable, that connection works (allows me to lock and unlock the car). So should be clean enough for the DMMs

 

Hmmm. If the car is locking and un locking that could blow the 400mA fuse.

 

I haven't tried unlocking with the DMM in place - out of curiosity, that shouldn't be able to blow the 10A would it? Since I've only been using the DMM on that setting. Just seeing if the car is blowing the fuses right when I put it line (even with my limited knowledge I would assume my battery would be dead right away if that amount of power is going through it)

 

Batteries have a surprising amount of capacity. Enough to weld with, even. 10A is nothing to them.

I don't think door locks would pull enough to blow a 10A fuse, but 400 mA ( aka 0.4A) would be pretty easy.

 

There's definitely something wrong, as the normal "resting" draw on the battery should be in the 20-30 m amp range; the fact that you show nothing tells me there's an issue somewhere.

 

So since you have a bunch of meters, here's what I would do.

1) Set one of them to read Resistance (ohms)
2) Set the one you want to read your current with to DC mA
3) Connect their leads together.

You should see something low on the Resistance meter - 3 ohms or so, which is generally teh contact resistance of the probes. On the meter set to read current, you should see a little tiny bit of activity - less than 1 mA.

If thats true, then your current meter is good and its time to call an exorcist.

 

I agree, that's why I am so confused

like this?

 

Looks like your 10A fuse is blown on the left meter.

Move the red lead on the left meter to the mA/uA plug and see what that one says about the 400mA fuse.

 

Same thing - just with the decimal moved over one spot. I guess it's blown too? I'm going to try the 77 see if that one is working

 

Yep, the big M next to the Omega (aka horseshoe), means Mega, which is 1,000,000 ohms. So you've got 1,553,000ish ohms of resistance, aka an open circuit.

 

Heres the 77. Says OL on both

 

Yep, those fuses are toast too. OL is code for 'more resistance than I can measure', aka, an open circuit or a blown fuse. You'll get the same reading if you just disconnect the leads on the meter measuring resistance and hold them apart. Touch them together and you should get some low resistance number.

 

As an aside, this is why a lot of us always put our meters away with the leads connected to the Volts/Ohms side. Its super easy to blow fuses when you go measure a voltage and they're plugged into the A or mA side. My meter even beeps at me angrily if I have the leads connected to current ports but I've got it set to voltage.

 

Jesus, and I just tested the old 87 and they are blown too.

So, new fuses all around



What are the chances that I came into 3 flukes and 1 cheapo with blown fuses? Not surprised by the older 87 that has been on an electrofishing boat forever. The 2 others from my stepdad (maybe blown since he probably just uses the ohm setting more often around the house?). And maybe the new one since its cheap?

There must be something happening when I connect the DMM inline. Maybe I'll make something like this and test this way

https://www.youtube.com/watch?v=B__DqK90IIc&feature=emb_logo

 

I pulled a nice benchtop meter out of a dumpster for free. Only thing wrong with it was a blown fuse, so I'm not at all surprised. 90% of the time people just read volts or ohms anyway.