Help finding a short, Who's good at ELECTRICAL???

[Nasty-LSX]

Let me start of by saying this truck(1985 K20) is unhacked, all in factory order,factory stock.
I have a battery draw. If I let it sit more than a day the battery gets low enough that I need
a jump start. I have to disconnect the battery every nite so it will start the next day.


Here is the problem, I have seen a ton of videos on finding a short. My problem is When I disconnect
the Neg cable and use my multimeter (just like in the video) I get 0.00 on the multimeter. Well as you
know thats showing there is no draw and everything is in good working order. What other option do I
have to pinpoint this issue?. This video is very clear with the multimeter, Almost every video out there
is the same to trace a short, but none say what to do if your getting 0.00 on the multimeter

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[fast 99]

Try using a test light in series with either battery cable. If it lights =draw. Another way is amp scale on MM in series, however if draw exceeds internal MM fuse it will blow. 3rd way is with a shunt. But usually, one if the above methods should turn up something. Others will come along with additional suggestions.

 

[NC595]

Just to clarify, you're definitely setting it to DC Amps, and not DC V, right? I only ask because I've made that mistake more times than I care to admit!

To elaborate on the video, you're putting your meter in series with the negative cable and the battery and the meter should be showing the amount of current headed to ground through the meter. Volt meters work in parallel, amp meters work in series.

That being said, I'd definitely start with what Fast 99 says above. If you're seeing the current read 0.00 while in series or other indications of zero-draw, then there's a possibility what you're looking at is intermittent and just not present when you're using the meter. I defer to those more experienced than me at that point though.

Hope this is helpful! Lets see how it plays out.

 

[Grit dog]

You don’t say what setting, V or A you’re using. To my understanding you’ll always “see” 12V across the neg battery post to ground. That is the voltage potential of the battery.
To check for a draw, you measure current. IE amps.
A draw on the battery connects the + to ground, completing the circuit.
Unintentional draws do this as well.

You need to measure amps across the neg to ground.
Example (old vehicles with no intentional draws like stereo memory or other electrical components)
The 86 K20 has a parasitic draw. Has for a while. Not sure if since we bought it or if it’s something I added. I suspect it’s the Chinesium headlight relay kit I bought. Because the year plus I had it apart doing paint and body it would keep an old refurb battery alive amazingly. Now it will kill a good battery in a couple-three months ish.
It has a 40mA draw (0.04A). But it won’t light a test light. However opening the door (dome lights) will light a test light.
It shows 12v across neg to ground though as it should.

The 77 c10 for comparison has 0-1 mA draw (basically zero). Still shows 12V across neg post to gnd. Doesn’t light a test light on the same test (obviously) but does if the dome light is on.

If you’re losing the battery in 1-2 days it’s a significant draw. I’d think it would light an old incandescent test bulb. It will certainly show up on a multimeter. My guess is 100s of mA or possibly a full amp or more draw. If you have a good 80-100 ah battery it would take a 1 amp draw to draw it down 50% in about 2 days. (If I’m mathing right). And 50% is basically dead. Lights may glow but it won’t crank.

 

[Grit dog]

Try using a test light in series with either battery cable. If it lights =draw. Another way is amp scale on MM in series, however if draw exceeds internal MM fuse it will blow. 3rd way is with a shunt. But usually, one if the above methods should turn up something. Others will come along with additional suggestions.

Test light requires a healthy amp draw. Remember what is being tested is the current flowing through the chassis (like a live short). It’s like the chassis is the positive post of a “battery” but it’s the stray voltage going to ground where it shouldn’t. (Been a while since my EE classes though…lol I’m old)
OP could be pulling enough amps to light a test light. Test light is for crude measurement of a pretty significant short.
To the other suggestion by somebody. It’s likely not an intermittent short if it’s repeatable as @Nasty-LSX alluded to.
Regardless it WILL be visible on a multimeter. Not sure why it isn’t for @Nasty-LSX.

 

[Nasty-LSX]

Just to clarify, you're definitely setting it to DC Amps, and not DC V, right? I only ask because I've made that mistake more times than I care to admit!

Thanks NC595. Yes I followed that video to a tee. Made sure all was correct since I cant get anything over 0.00

 

[Nasty-LSX]

Try using a test light in series with either battery cable.

is this what your talking about? I get 12.2 volts when I go from neg cable to neg batt post.

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[Nasty-LSX]

You don’t say what setting, V or A you’re using.

Im doing it exactly like the video shows to do it, and hundreds others, Checking in 10 amps on meter.
I am also not using a cheap 10 dollar meter, just dont understand why it wont show a draw

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[Nasty-LSX]

The batt is only 4 month old. The truck did it with the previous battery
so I know it is not a bad battery. As long as it stays disconnected I keep 12.2 volts.