OK, I've been fighting a drain/Charging/alternator issue, and I'm trying to properly remove variables. I suspect the battery, but the MASTER mechanics (lol) at Autozone say it's good. ...anyhow, the problem itself is for another thread, but this is simply to be sure I'm reading my multimeter properly.

OK.

I'm looking to see if I have a drain on the system with everything OFF. I disconnected the negative cable, and (obviously) putting the multimeter in the line to read how many amps/milliamps I'm drawing. I've read for newer cars, you don't want to see over 50 Milliamps, but I suspect it would be less for our cars.

I first connected the positive lead to the 10A terminal and set the multimeter to the 10A scale. No reading whatsoever. 0.00 I expected this. Then I moved the lead back to the 200mA "max" terminal, and set the dial to 200m, and I read 4.3 ....then moved the dial to 20m, and read 4.32 Now I'm not real good with electronic circuits, but this all appears to make sense, and at the very least, it appears the multimeter is reading properly. Stop me if you disagree.

.....so here's the million dollar question: Is that 4.32 MILLIAMPS????? Logic would suggest that it IS in fact only 4.32 Milliamps. It's not 43.2 Millamps? Not 432.00 Millamps?

The reason I ask is because I guess I was expecting to see a number OVER 50 milliamps. When I saw 4.32 I thought maybe I was reading it wrong. I hope I'm right. I hope there is NOT a draw that I have to chase down. 4.32 milliamps would be just fine with me.

 

Just so we don't go off on a tangent here, I have two alternators, both charge just fine, both check out fine, and one is new so I don't see that being the problem. AND....when I tested amp draw on the battery, it was freshly recharged. This thread is intended to clarify that I am in fact reading the multimeter properly, and can focus my attention elsewhere.

 

If your using a digital meter, you should be at 4.32 mA no matter what your max setting is.

 

Exactly what I was thinking. So if newer cars can potentially (and safely) draw up to 50 Milliamps, and my old 89 is reading only 4.32 milliamps, then I can probably cross a short off my list. I really suspect the battery. It's been beaten on over the years, but when they said it tested good, it threw me off. I may just swap batteries with Trailblazer and see what happens, just to be sure.

Thanks,
Chris

 

OK, see....this is what's throwing me off. I just watched this video.


He also states you shouldn't see more than 50 milliamps, BUT.....when he puts the meter on the battery, it's reading only 3.6 and he says it's way too high, suggesting a drain. ....which of course suggests that it's actually 360 mA, not 3.6 mA.

....so back to my reading of 4.32 ....is that 4.32 ma, or 432.00 ma? I can't seem to get a clear answer anywhere. I have a reading of 4.32 somethings. 4.32 pounds of spaghetti? 4.32 gallons of water? 4.32 amps? Milliamps? The difference is HUGE, BUT.......no one knows what unit of measure that 4.32 is!

 

Easy - it's 4.32 milliamps. If it was 432 milliamps, the meter on the 200mA or 20mA ranges would read Overload. Also the 10A range would read 0.4.

Not enough to flatten your battery in any meaningful time period.

 

yeah, that's what I thought, but that video threw me off. Maybe that guy had something set a certain way that I missed.

Thanks.

 

The guy on Youtube set his multi-meter to the 20 Amp scale. That means that the multi-meter will be reporting any numbers in Amps. His video shows approx 3.5 so that means he's reading 3.5 amps.

If you set your multi-meter to 200 mA, it means that any readings you will be getting are in milli-amps and the maximum it can display is 200. So a reading of 4.32 will ALWAYS mean 4.32 mA. When you set a multi-meter to a certain setting, you do not have to recalculate the result. Milli-amps mean milli-amps, amps mean amps. It is simple and clear. If I found a multi-meter that would make me recalculate every result to some strange scale, I would give it away.

So now to your result, 4.32 mA is expected draw on the battery and will not drain it overnight. For that, you would need to see a few amps to drain the battery.
Simple math here: if your battery is rated at e.g. 40 Ah, that means that it can supply X amps over Y hours. It could be 4 amps over 10 hours, 10 amps over 4 hours or even 1 amp over 40 hours. So from the Youtube video, a 3.5 amp draw would definitely kill the battery overnight.

One more clarification: you want to use the word "draw" or "drain" instead of "short". Short implies a short circuit of power to ground (without any device or load in the path) and usually has damaging consequences and kills power fast and can cause fire. Drain or draw is usually small and happens while some devices are drawing and using power.

Sorry, I didn't mean to type so much, I just wanted to clarify.

 

Type all you want! ....I appreciate the info. I admit that my electrical knowledge is the bare minimum of what I need to get by!!!! Any knowledge helps!!!!!!!!

Thanks

 

Hi Chris, The fellow in the video had his meter set to the amp scale, not mA. He was reading 3 amps, which is a draw. I think your getting the two amps mixed up possibly? This may help; http://www.convertunits.com/from/milliamps/to/amps 1000 milliamps = 1 amp

 

Yep. That's exactly what I did. Everything checks out. No drain.