To the Power Probe Users

[tankmech77]

Hey Guys, as the title states this is for all you Power Probe users out there. I just picked mine up a couple weeks ago after drooling over it for a few years. Company paid too!

So, here's the setup, then the question, apologize ahead for the length.

I was diagnosing a scissor lift that ended up being wired up wrong. Its a 6vdc x2 for total 12vdc system. problem was as I was attempting to reattach the main negative to the battery post it would arc flash pretty badly. So I break out the schematics, find my hots and grounds and start probing away to find where I shouldn't have power but do...according to the probe, all grounds cause the green "-" symbol to illuminate and 0.0vdc to read on the display. My hot spots all show 12 to 13vdc and the red "+" sign.
So it says all is good.

Now another guy, old school guy, doesn't trust new fangled technology and gets his trusty 36 volt test lamp...EVERY single ground spot he touch light the lamp up. 36 volts so wasn't that bright, but fact is, it lit, so there's clearly quite a bit of power there. A 12v battery will light it up just enough to be visible, and this was lit up like a normal 12 volt test lamp.

Assuming you all can tell what the question is, but just in case, how the hell can 2 probes that are "when all said and done" essentially the same thing give such different results? OR even better question, is there something I may have done incorrectly? that was 1st time ever using the probe and still learning exactly how it works. for what its worth,

I was hooked up to 1 battery, pos to pos neg to neg. he of course was hooked to the neg.

appreciate all the answers in advance.

 

[firebox40dash5]

Its a 6vdc x2 for total 12vdc system... I was hooked up to 1 battery, pos to pos neg to neg.

Um... if it's got 2 6V batteries in series, and you were on one... then the PP was getting 6V. I've never tried mine on a 6V battery, but I know a discharged 12V battery makes it grumpy.

Now another guy, old school guy, doesn't trust new fangled technology and gets his trusty 36 volt test lamp...EVERY single ground spot he touch light the lamp up. 36 volts so wasn't that bright, but fact is, it lit, so there's clearly quite a bit of power there. A 12v battery will light it up just enough to be visible, and this was lit up like a normal 12 volt test lamp.
The bold confuses the hell out of me... which is it? If your 2x6V setup made a 36V test lamp light up like it should, you got problems.


Assuming you all can tell what the question is, but just in case, how the hell can 2 probes that are "when all said and done" essentially the same thing give such different results? OR even better question, is there something I may have done incorrectly? that was 1st time ever using the probe and still learning exactly how it works. for what its worth,
I wouldn't call them the same thing... one's a light bulb in a screwdriver with a wire coming out of it, the other's an overgrown logic probe.

As for answers... which negative terminal was he on? My only guess would only apply if he was on the "middle" ground post (the one linked to the other battery's positive), and even then it doesn't really make sense. It's been a while since I messed with series batteries.

 

[tankmech77]

True on the differences,

yes, I was on only one battery, and my probe was getting 6 volts, but since the things I was probing were hooked up normally it was reading 12 on the hot sides...
ACTUALLY, I was on the middle neg and the "last" pos...

yes, he was on the "middle" neg.

NO IDEA how that got bold, I didn't intend on anything being bolt BUT yes that' my point, he was on the middle neg and his light was lighting up. obviously a problem,

thing is, his light lighting up was correct. the unit had its drive ecu replaced and had been wired backwards. that's why the "main" ground was arc flashing. so basically I knew why his light was lighting was lighting, what I'm really asking is, if when probing a ground that CLEARLY had power sitting at it when it shouldn't have, why the probe showed - with 0.0 vdc like everything was fine?

 

[firebox40dash5]

True on the differences,

yes, I was on only one battery, and my probe was getting 6 volts, but since the things I was probing were hooked up normally it was reading 12 on the hot sides...
ACTUALLY, I was on the middle neg and the "last" pos...

yes, he was on the "middle" neg.

NO IDEA how that got bold, I didn't intend on anything being bolt BUT yes that' my point, he was on the middle neg and his light was lighting up. obviously a problem,

thing is, his light lighting up was correct. the unit had its drive ecu replaced and had been wired backwards. that's why the "main" ground was arc flashing. so basically I knew why his light was lighting was lighting, what I'm really asking is, if when probing a ground that CLEARLY had power sitting at it when it shouldn't have, why the probe showed - with 0.0 vdc like everything was fine?

I made that part bold because it confused me... I wasn't (I'm really still not?) sure if you were saying the test light barely lit up, or it lit up "like a normal 12V test lamp" which implies to me it lit up like it had 36V.

Anyway... I'm too lazy to draw myself a diagram, and I can't work out what should be going on vs. what did go on in my head. All I can figure is that the misread had something to do with you only being on "half" the circuit by connecting to one battery, assuming nothing else you were messing with is similarly wired to just one battery for 6V power. That's all I can make sound plausible in my head. I doubt it was caused by only powering it with 6V, my guess would be something to do with how the logic probe part of it does its thing. I'm assuming you fixed it though, and probably don't want to break it again for gits and shiggles, so all I can say is I'd bet if you were on the "outside" terminals (the full 12V as fed to the machine) it would have worked right.

 

[tankmech77]

Heh, aah that makes sense, ok...and I can see the confusion in my explanation also. to simplify, the light was fairly lit up but definitely NOT all the way being a 36 volt light,

but yeah the actual problem I got fixed up. to be honest I'm always up for learning from my mistakes so if it wouldn't piss the boss off or risk (thank god this didn't happen) blowing up a 1000+ drive ecu Id try it again to learn from it.

You're also correct in saying nothing else was wired up like the probe, everything else was wired up the way it should've been, well...wired for 12 vdc anyway

you could be right about the "inside" vs. "outside" terminals though. I think when I get a few minutes I'll take a machine i know is wired correctly and plug up to the outsides and see what happens.