How do I check my ground resistance w/ a DMM?
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Silver Member Username: Jonez788Marshalltown, Iowa Post Number: 184 Registered: Jun-04 | I've read a lot about seeing how many ohms are at my grounding spot. However, I have no idea how to test that. I have a DMM, do I just switch it to ohms? Where do I put the probes at? Thanks for any replies. |
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Silver Member Username: Van_manBoston South, MA Post Number: 671 Registered: Mar-06 | yes, set it to ohms. When you touch the two probes together it should read Zero. No resistance. Put the probes on a speakers terminals, it should read ~ 4 ohms or ~2 ohms if it a 2ohm coil. go from the amps Neg to grounding point, You want the lowest number possible. Zero is the best. check between battery neg and chassis, alt case and chassis, alt case and bat neg terminal. |
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Gold Member Username: Dustin3Tigard, Or U.S. Post Number: 1812 Registered: Oct-05 | do u just put it where it is grounded at? like if a bolt is holdin down ur ground, can u just put the two probes under there? |
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Silver Member Username: Van_manBoston South, MA Post Number: 672 Registered: Mar-06 | Put 1 probe on the bolt, the other probe at the amp neg. This will tell you the ground wires ohms to ground.  |
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Gold Member Username: Dustin3Tigard, Or U.S. Post Number: 1829 Registered: Oct-05 | wuts the point of checking the other grounds? just to see if u have a good one? i mean the batt and alt ones |
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Silver Member Username: Van_manBoston South, MA Post Number: 676 Registered: Mar-06 | yes, Wires may look ok, but may be corroded on the inside. My engine to chassis ground strap looked fine, a flat, 1.5" bare copper wire about 10"long, but when I put the meter to it it was over 6 ohms..I ran a new 1/0 next to it and checked alt to chassis agaian. Now it is at zero  |
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Gold Member Username: Dustin3Tigard, Or U.S. Post Number: 1835 Registered: Oct-05 | ^^ thanks. i might be doin that soon. so if i were to do the batt, i would put it on the batt neg terminal, then the other probe to the spot where its grounded at?> wut the point of doin the alt case (dont know where that it...) to the batt? |
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Gold Member Username: Dustin3Tigard, Or U.S. Post Number: 1836 Registered: Oct-05 | does this also tell u if u have a good ground if it reads zero? |
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Silver Member Username: Van_manBoston South, MA Post Number: 677 Registered: Mar-06 | yes, i had explained it in more detail but got lost posting. so heres a link to research. Look at section 37, but I suggest reading all sections http://www.bcae1.com/ |
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Silver Member Username: Jprix82Post Number: 595 Registered: Jan-06 | So this is a way to check if you have a bad ground? |
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Silver Member Username: Jprix82Post Number: 596 Registered: Jan-06 | I checked my amps ground today,whith my DMM set to ohms/200 it read 00.2. Is this good or bad? |
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Silver Member Username: Jprix82Post Number: 597 Registered: Jan-06 | bump |
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Gold Member Username: Suleman36Maryland U.S.A. Post Number: 3924 Registered: Feb-05 | Anything under 1 ohm is fine. |
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Silver Member Username: Jprix82Post Number: 598 Registered: Jan-06 | Hmm well i have eng. whine noise in my system,so if the ground is good it must be the rca's then. |
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Silver Member Username: Van_manBoston South, MA Post Number: 682 Registered: Mar-06 | Try a temp set of rcas, Then go find the weak ground. 99.99% it will not be RCAS |
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Silver Member Username: Jprix82Post Number: 599 Registered: Jan-06 | since the ground for my amp reads 00.2 that means its good right? Now i have to check my HU's ground. |
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Silver Member Username: Jprix82Post Number: 601 Registered: Jan-06 | Btw my rca's are made by Boss.Thats most likly my problem.. |
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Silver Member Username: Van_manBoston South, MA Post Number: 684 Registered: Mar-06 | You want to check all your grounds. Just for giggles, get a long thisk wire like 4 awg and run it straight from the battery neg to the amps negitve. If the noise goes away, its the ground. If it stays, its the rcas. |
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Gold Member Username: Dustin3Tigard, Or U.S. Post Number: 1912 Registered: Oct-05 | remember, thats just for giggles |
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Silver Member Username: Jprix82Post Number: 603 Registered: Jan-06 | would the lenth(~17') of the wire from the battery grd to the amp grd cause any noise by itself? |
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Silver Member Username: Van_manBoston South, MA Post Number: 686 Registered: Mar-06 | Just for giggles would be hooking up the neg from bat to amps pos. |
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Silver Member Username: Van_manBoston South, MA Post Number: 687 Registered: Mar-06 | no joe |
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Silver Member Username: Jprix82Post Number: 605 Registered: Jan-06 | thanks marc,J/W why does everybody sam make sure your ground wire is no longer than 3'? |
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Silver Member Username: Jonez788Marshalltown, Iowa Post Number: 186 Registered: Jun-04 | It really doesn't matter how long your ground cable is. That's just what every installation tutorial goes by |
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