Grounding Issue in 96 Explorer?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=85226
Printed Date: May 02, 2024 at 2:14 PM
Topic: Grounding Issue in 96 Explorer?
Posted By: otter
Subject: Grounding Issue in 96 Explorer?
Date Posted: November 06, 2006 at 12:26 PM
Hey all,
I am in the middle of an install in a 96 Ford Explorer, and have run into something I have never seen before. I have run the power, remote and RCA wires, but I am having a heck of a time finding a good place to ground. I checked all bolts that are close to where the amp rack is mounted with the lowest reading being in the 25+Ohms resistance level (checked using a multimeter hooked between the potential grounding point and the batt. neg. terminal) I also ground all of the paint off of an area under a seat (on the floorboard), and tried making a grounding point with a self tapping screw. same result, resistance of 25+/-ohms.
all of my testing was done with a multimeter and wire that in combination had a resistance of .01 ohms.
what is going on here? I have never seen anything like this. I really would like to avoid running a direct ground back to the battery Neg terminal seeing as that copper prices are through the roof!
thanks in advanve for the help
Ryan
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Replies:
Posted By: Custom_Jim
Date Posted: November 06, 2006 at 2:23 PM
How is the battery negative to body ground ?. Normally you have a big wire going between the battery negative and the engine but since it's on rubber mounts it's tied very poorly to the body of the car (potential but poor grounds are shifter cables and emergency brake cables). This is why there is another connection between the battery negative and the body or from the engine to the body. Slowly work away from having both meter leads on the battery and see where the drops are occuring the further you move the one test lead away from the battery. Jim ------------- 1968 Chevy II Nova Garage Find 2012
1973 Nova Custom
1974 Spirit of America Nova
1973 Nova Pro-Street
Posted By: aznboi3644
Date Posted: November 06, 2006 at 4:20 PM
Um...exhisting bolts aren't good grounds....just find a clean spot and drill a hole and use a nut and bolt
Posted By: sparkie
Date Posted: November 06, 2006 at 6:58 PM
I hope you are testing the ground with a digital meter and that you have the battery disconnected when you take the readings. You can't check resistance in a circuit or vehicle that is hooked up. Disconnect the battery and re-test. If you wish to check it with the battery hooked up, you need to set your meter to DC voltage and do a voltage drop test to check the ground. Place one probe on a good ground ( where the battery is grounded to) and the other probe on your system ground. Ideally, you should get a reading of less than 0.5 volts.
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sparky
Posted By: otter
Date Posted: November 06, 2006 at 7:50 PM
Custom_Jim wrote:
How is the battery negative to body ground ?. Normally you have a big wire going between the battery negative and the engine but since it's on rubber mounts it's tied very poorly to the body of the car (potential but poor grounds are shifter cables and emergency brake cables). This is why there is another connection between the battery negative and the body or from the engine to the body. Slowly work away from having both meter leads on the battery and see where the drops are occuring the further you move the one test lead away from the battery.
Jim
thanks for the reply! I actually already upgraded that wire thingking the same thing. I added a 4ga wire from batt neg. to chassis ground. -------------
Posted By: otter
Date Posted: November 06, 2006 at 7:52 PM
aznboi3644 wrote:
Um...exhisting bolts aren't good grounds....just find a clean spot and drill a hole and use a nut and bolt
thats what I did. I was simply stating that I checked all of the bolts to see if for some reason the floor board was not a good ground (not sure why this would happen, but it is an older car, and you never know what someone has done before) so I simply checked them, and then made my own ground. -------------
Posted By: otter
Date Posted: November 06, 2006 at 7:57 PM
sparkie wrote:
I hope you are testing the ground with a digital meter and that you have the battery disconnected when you take the readings. You can't check resistance in a circuit or vehicle that is hooked up. Disconnect the battery and re-test. If you wish to check it with the battery hooked up, you need to set your meter to DC voltage and do a voltage drop test to check the ground. Place one probe on a good ground ( where the battery is grounded to) and the other probe on your system ground. Ideally, you should get a reading of less than 0.5 volts.
wow, I never knew that. I have been doing my tests (as I always have and have seen shops do) with the battery still hooked up. I'll give that a try when the car comes back. I think I am going to finish the work on it next week. However, I know that the ground is bad because I fired the system up and there is noise in the system. Where else should I check for a place to ground? -------------
Posted By: Mad Scientists
Date Posted: November 07, 2006 at 6:52 AM
I doubt that 25 ohm reading is correct; if it was, nothing electrical would work on the body. Measure voltage from the same two points.. as was pointed out earlier, you shouldn't see more than 0.5 v. Jim
Posted By: otter
Date Posted: November 08, 2006 at 10:44 AM
unfortunately, I have checked it, and re-checked it. has anyone done an install in one of these cars? If sowhere did you ground at?
Posted By: Custom_Jim
Date Posted: November 08, 2006 at 11:31 AM
Otter, Have you tried yet with the meter having both test leads on the battery and then moving one away from the battery to the next connection ?. Is it possible the meter is defective or set wrong ?. I would maybe do these steps: Disconnect the positive terminals off of the battery. Place both meter leads on battery negative terminal (should read 0 ohms and if not then zero the meter, try a new battery, or write the figure down it is showing but this should only be maybe 1-2 ohms tops as a higher reading would lead me to believe a defective meter and or test probes) Now leave the one test lead on the battery negative post and take a 15' or so chunk of 16-18 gauge wire and with the other test lead connect this to one end of the wire and connect the other end of the wire to the battery negative terminal. The ohm reading should be the same or just a tad higher. Now with the one end of the wire remove that from the battery and trace down where the battery negative cable connects to the body of the vehicle and connect it there and note the reading. Now remove it from there and try a grounding spot under the dash. Now move it even further away towards where you have the amp and where you want to make a ground connection. At some point the readings will jump to the high reading you had. Between this point and the point before should be the problem and then this can be addressed. If all else fails, run a ground from the battery to the spot you want to grounfd the amp to. Most vehicles are spot welded together and this should allow a decent electrical path but maybe somethings funky like the metal is poor for conducting or the welds are not enough or improper. Using the meter to find where the resistance changes is just like seeing how there are voltage drops through different things like connections, fuses, cabling, and so on. You just have to do it in an organized manner and not in a random fashion. Jim ------------- 1968 Chevy II Nova Garage Find 2012
1973 Nova Custom
1974 Spirit of America Nova
1973 Nova Pro-Street
Posted By: otter
Date Posted: November 09, 2006 at 10:09 AM
thanks jim, I'll try that. I have just been testing randomly. I'm sure that the readings are correct, I have already tested the meter in the way that you described above
Posted By: master5
Date Posted: November 09, 2006 at 11:39 AM
Heres a quick way to tell if theres a grounding issue with your vehicle... Of course make sure your meter is ok but you can use the votage setting for this. Put the meter on DC to measure 12v. Touch the negative probe to the battery terminal (make sure it's clean), and touch the positive to various metal such as the hood, fender, block, shock tower, alternator etc. If you get any voltage readings you found the culprit. I had a car once show 12v+ when I touched the hood doing this same test. That can't be a good thing. Simple wire (ground strap from hood to body) fixed it. -------------
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