I have been trying to figure out my EPS and have found that I have a ground issue. Has anyone measured the ground ohm ratings from different points on the car? I've found that continuity on an NSX has a different rating than most cars. I have also found several of my grounds reading 4.0-6.0 ohms. Correct me if I'm wrong, but isn't this a big ground problem? A proper ground on most cars is .02-.06 correct? I was unsure if the aluminum body had some sort of effect on this or what but almost all of my grounds are above 2.0 ohms all the way up to 8.0ohms. Do I just need to do a major ground kit using the negative battery cable or is this normal for some reason on the NSX? I could understand it if it was a carbon fiber body and subframe but it doesn't make sense on aluminum. Thanks for any help in advance.
Ground questions and ohm readings. Please help.
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6 - 8 ohms is not good but I would suspect the meter or just dirty measuring points over an actual grounding problem.
I have no idea what typicial readings should be. Which grounds are you looking at? Make sure your meter reads 0 with the probes touched together.
Yep. 0 when touched together and .01 through .03 from post to post on the battery.
I have checked nearly all the grounds and have reading written down in a notebook at work. A couple were nearly broken and the one attached to the battery was broken. Everyone that I've found that looks bad, I replaced. Readings are getting better but still around 5-6.
I have checked nearly all the grounds and have reading written down in a notebook at work. A couple were nearly broken and the one attached to the battery was broken. Everyone that I've found that looks bad, I replaced. Readings are getting better but still around 5-6.
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Aluminum is a very good conductor of electricity, but aluminum oxide is a good insolator. Look for signs of oxidation around connections.
Gary
Gary
Thanks for the insight. I have realized that as of lately. I have found a lot of corrosion and have repaired three grounds. I just need to know what readings are normal so I will know what is on par with the tolerances of the cars electronics. Will the electrical trouble shooting manual tell me? If so, I guess I could buy one.
Across a ground connection you should have 0 or close to 0 ohms or no more then + .1 of what the meter showes with the probes touched together.
Then I have an issue somewhere. From the neg post to the main two grounds under the hood attached to the passengers side rail is showing 3.0 and 2.5. I honestly thought that it could be reading that high due to the all aluminum body and thought it might be correct on an NSX because I have seem the issue on a non aluminum car but haven't studied grounds on an NSX because I never had the issue on the other three I've owned.
Well any ideas on where to start my search?
Well any ideas on where to start my search?
I'll check mine tomorrow if i get it back from the body shop. I'll let you know.
Start at the negative cable attached to the battery. If all of your readings are above what they should be, the only thing in common (excuse the pun) is that they all go back to the battery ground terminal. That battery connector has been a source of many discussions here and is a known problem.
Good Luck!
Thanks very much. I will replace the terminal to start with. Is it recommended to replace the whole cable?
There is a product called No-Ox (or something like that) used in house wiring that is used to prevent oxidation when joining aluminum and copper wire. I used it about 20 years ago when hooking up an electric range to aluminum wire, and it has worked perfectly. The 50 amps or so for the stove is not unlike some heavy currents in some grounds in a car.
It seems to me that such a product might be benficial on ground connections in an NSX. It should be available at any good electrical supply house.
Because of the electric potential generated at the junction of dissimilar metals, measurement with an ohmmeter may not be accurate or appropriate. A better method is to measure the voltage drop between battery or engine ground and the point of concern. As an example, 14 gage wire is .0025 Ohms per foot. So, for a 15 foot long 14 gage ground lead (.0375 Ohms) carrying 20 amps, one might expect about 3/4 volt drop in that lead.
For the lead in which you measured 5 or 6 Ohms, even if the +12V lead was zero Ohms, you could only draw about 2 amps with a short circuit! So, yes, something like .02 Ohms might be a more typical value for a medium current ground. For the starter, which draws hundreds of amps, the ground cable is much thicker and its resistance much lower.
I realize the voltage drop measurement method takes more effort because you need long leads to measure between two points than can be 15 feet apart. And you also need either an inductive current probe, or you need to directly measure the ground current with your meter. But, with dissimailar metals, that's the best way to get an accurate measurement.
It seems to me that such a product might be benficial on ground connections in an NSX. It should be available at any good electrical supply house.
Because of the electric potential generated at the junction of dissimilar metals, measurement with an ohmmeter may not be accurate or appropriate. A better method is to measure the voltage drop between battery or engine ground and the point of concern. As an example, 14 gage wire is .0025 Ohms per foot. So, for a 15 foot long 14 gage ground lead (.0375 Ohms) carrying 20 amps, one might expect about 3/4 volt drop in that lead.
For the lead in which you measured 5 or 6 Ohms, even if the +12V lead was zero Ohms, you could only draw about 2 amps with a short circuit! So, yes, something like .02 Ohms might be a more typical value for a medium current ground. For the starter, which draws hundreds of amps, the ground cable is much thicker and its resistance much lower.
I realize the voltage drop measurement method takes more effort because you need long leads to measure between two points than can be 15 feet apart. And you also need either an inductive current probe, or you need to directly measure the ground current with your meter. But, with dissimailar metals, that's the best way to get an accurate measurement.
Ox-Gard Aluminum wire anti-oxidant
http://electrical.hardwarestore.com...x-gard-aluminum-wire-anti-oxidant-601592.aspx
It couldn't hurt, I would use it on the battery cables to chassis. Yes, voltage drop will help determine where the problem is.
Interesting to see if this is the problem with your EPS.
http://electrical.hardwarestore.com...x-gard-aluminum-wire-anti-oxidant-601592.aspx
It couldn't hurt, I would use it on the battery cables to chassis. Yes, voltage drop will help determine where the problem is.
Interesting to see if this is the problem with your EPS.
