Car Audio Central - Ultimate Car Audio Forum and Community

I agree that you want readings to be as close to rael world conditions as possible, so all factors would be considered when measuring chassis resistance. Zeroing the meter with the non inductive leads is a good plan as well.

[quote="Basstronics"]To measure tru resistance the item to be metered must be out of the circuit. Otherwise your measuring the FULL resistance of the whole circuit.

So unhook every wire off your explorer then measure ]

not true at all!

If that was an issue with the DMM, it would also be an issue with the amp - so it needs to be measured.

To measure tru resistance the item to be metered must be out of the circuit. Otherwise your measuring the FULL resistance of the whole circuit.

So unhook every wire off your explorer then measure





















As you can guess this is not feasible

Fishy wrote:Lol, why so defensive?

I never said it would be less than 2/0 gauge and my numbers are probably garbage anyways. I don't think there's an easy way to measure resistances that low without a high current meter of some sort.

-Fishy

lol, i wasnt being defensive, wasn't sure if i said I was using 2/0ga wire or not, didn't remember.

now if i woulda said... I WAS USIN 2/0 GA WIRE BIOTCH!!!!!

it woulda been another story! lmao

Lol, why so defensive?

I never said it would be less than 2/0 gauge and my numbers are probably garbage anyways. I don't think there's an easy way to measure resistances that low without a high current meter of some sort.

-Fishy

Fishy wrote:Well I've come to the conclusion that my multimeter is completely useless for measuring chassis resistance. Its a $50 Micronta and does not like anything under 1 ohm. Are those expensive Fluke deals any better at measuring resistances on the order of milliohms?

I count vouch for the numbers, but it looks as though my Explorer's chassis resistance is about the same as a 20 ft piece of 1/0 gauge. In other words the reading I got using that 1/0 was as probe wire was about twice what the 1/0 itself measured.

-Fishy

I put in there that I was using 2/0ga wire didnt i?

I'm not certain how 1/0ga would react.

Well I've come to the conclusion that my multimeter is completely useless for measuring chassis resistance. Its a $50 Micronta and does not like anything under 1 ohm. Are those expensive Fluke deals any better at measuring resistances on the order of milliohms?

I can't vouch for the numbers, but it looks as though my Explorer's chassis resistance is about the same as a 20 ft piece of 1/0 gauge. In other words the reading I got using that 1/0 was as probe wire was about twice what the 1/0 itself measured.

-Fishy

I guess it does vary by car, but I thought I read somewhere(RC I think) that a typical chassis ground was equivalent to 1/0 gauge. I always wanted to measue the chaasis resistance of my Explorer, but was wondering how you would do that. I guess you'd have to measure the resistance of your extra long probe leads and subtract that from the value you got. I thought of using an analog meter and zeroing it with the leads intact, but they kinda suck when it comes to measuring very low resistances(not enough resolution on the gauge).

I really wasn't saying that a 2/0 ground cable wouldn't be better, but I don't think chassis grounds are as sucky as everyone thinks.

-Fishy

on an average car, a chassis ground is considered equivelant to a 4AWG cable.
This will vary from car to car though. In my case, it's probably a bit better, being all 1966 Detroit steel, and no rust. Modern cars are usually unibody or floating frame though, and a lot of fiberglass, relying on spot welds for most sectional joining. That's not an ideal connection as spkrman mentioned, unless you're reinforcing the frame and joining front and rear halves with frame connecting beams etc.. common to do on Fox body mustangs to stiffen the frame etc, but not a common thing for the average Joe to do.
If you're drawing thousands of watts of power, and using one or more runs of 0AWG of larger cable, it's worth considering running ground back to the battery or to the engine block ground point instead of relying on a bolt in teh trunk.
If youw ant to be sure, you can measure resistance to see what you're dealing with for a specific application.

smoker wrote:well for what its worth we have always grounded in the rear but usually upgrade the factory ground up front as well. minimum 4 guage wire up front to improve upon the factory ground.

have you ever done a very high power setup?

once you get some real juice goin body ground just doesnt do it.