Big 3 Grounds... Ohm reading unacceptiable?

[Volvowith18psi 10+ year member]

So, did the Big 3 this past weekend in 1/0 w/ Knu. Getting bored waiting on equipment to arrive, came across a video showing how to check grounds. So, I checked mine.... Roughly .8ish ohms after meter baseline subtracted. Terms soldered using resin core solder like in videos, sanded everything best I could with sand paper..

Now, This video I watched said he did a "voltage drop" test, using "Volts DC" connect Neg lead to neg bat term, pos to potential ground spot. Nothing should be over .2?? I checked mine using the "ohms" setting, and got my readings.... Everything I read online said to use the Ohms, not Volts DC. Anyway, mine are much higher then that. Should I do it again?

I used mostly factory ground spots. See pics. Should I just make new grounds w/ self tapping screws? (dont want to really de-paint 10 spots under the hood trying to find a spot under .2)

Ironically, the rusted nut near the dipstick, the one that got the worst sanding done due to the bolt, showed the lowest resistance>>

Thoughts?

Yay for pics. I did this in an apartment parking lot >>

Click to read more...

 

[All_Logix 10+ year member]

If the bolt you used goes directly into grade a steel and not like a plate of sheet metal that is welded to the steel frame, you should be fine. As far as the video goes, I have not seen it so I do not know exactly what is going on...but I do know that on way of measuring "resistance" is to measure the voltage drop between two points. If they were using the Volts DC, were looking into how much of a drop there was in voltage between the two points which is proportional to the resistance through Ohms Law. Where they said .2 is the most there should be it is very possible they meant there should not be anymore than .2 volts dropped between the points as opposed to the resistance taken. In a nut shell I think you are OK with using the factory bolt, given that this follows what I said in the beginning

 

[Volvowith18psi 10+ year member]

Thanks for the tips. Yea, after looking it over, the bolts do go into flimsy sheet metal. Ima have to pull it all off and do it again with better spots. I "borrowed" a metabo grinder / some wire and tiger discs from work to get a proper clean this time. Self tapping screws too. Little more difficult when you don't have strut housing bolts too readily accessible. Hopefully this time around will be better. Ill update with more pics once I get it changed.

There is the link to the video, however, I tried his method: Using "Volts DC" One probe to negative terminal, 1 to ground locations- The meter read nothing. Switched probes, nothing. The only way I got a reading was from using the "Ohms" setting... Meter is a calibrated Fluke True RMS Clamp/ Probe meter. Not sure why I got nothing using "Volts DC"....

 

[Volvowith18psi 10+ year member]

Edit: Sorry for double, stupid lag.

 

[Volvowith18psi 10+ year member]

Just wanted to update. Re-did everything, got the 90 out, much better resistance levels. Think I got a max of .01ohm once, checked at the actual metal to end of wire, not ring term to wire //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif Overall, think I gained .3-.4 charging volts. Big 3= complete.

 

[Jerhemy 10+ year member]

this a jeep?

glad you got your resistance down, when you run serious current through those lines, that high resistance coulda been a bigger issue!

 

[Volvowith18psi 10+ year member]

Yea, its in a 03 GCL.

 

[All_Logix 10+ year member]

just out of curiosity, when you tried the VDC setting, did you have the power wired up?

 

[keep_hope_alive Premium Member]

When I measure low resistance i insert a 10 ohm resistor in series, that way you are within the operating range of the meter. Most meters will lose accuracy at very low and very high restance. Note you need to calibrate by measuring the leads and resistor first, then measure the ground path, and subtract the distance.

 

[Volvowith18psi 10+ year member]

Tried with batt connected, batt disconnected, car running, car off etc.., 2 different Fluke meters, one is kinda older, and one Fluke 336.

I did also calibrate the meters by touching leads the leads. The 336 had roughly a .4, and my older one read .00 maybe .01- Used the .00 scale as the .000 scale was to sensitive. Before swapping, I read roughly around 1.4-5-6 neg term to old ground spot w/ the 336. Did not measure with my older one (didn't have access to it at the time).

When I re-did everything, I made sure to check the wire itself, all were perfect on the .00 scale (Checking my soldering job) hit every spot including the alt bracket with the 90 to shiny metal. New readings, nothing over .01. Same goes for my amp ground. All measured with the "ohm" setting on the meter.