I'm putting in an amp in my 86 coupe. Where is the best place for the ground cable in the back half of the car? Thanks for the help.

Craig

 

I can not answer your question but if you have a digital multi meter I can tell you how to find the best place for a ground.

 

Thanks for the relpy. I know how to check the ground. I just thought before I removed my carpet and looked for a ground I would ask here. Thanks!!


Craig

 

no problem

 

The best possible ground is a wire from the negative battery terminal back to the amplifier because that path does not share a path with other currents in the car and the voltage drop from the other loads won't be applied to the amplifier power wires. Usually you can do with a ground to the frame. Just keep in mind that a separate ground wire to the battery is a possible fix for what are called, "ground currents".

 

Please explain "ground currents".

 

I ran mine back to the battery as well.



jfb, did you want to say "ground loop" because I too never heard of "ground current"
The current through the ground is equal to the current going to the positive so if you use the same guage and same length of wire to the battery, you'll be just fine.

 

I ran my amp ground to the frame of my seat...it worked in my 85, and it's working so far in my 87....other than that spot, I would imagine if you ran it outside with the antenna wire, then grounded it on the same location the antenna motor is grounded, you might be ok...

 

EatRice,

could you explain what you mean by finding the best ground? Do you just take the multimeter and see which has the lowest voltage reading? Do you just take a AA battery hook it to the positive terminal and test the car?

Speaking of running a ground wire from the battery. I kind've like this idea. I really don't want to drill in my car unless absofreakinglutely necessary this time. Bad experiences. Anyhow, what about feedback? If you have a ground over 18 inches can't that act as an antenna?

Inquiring minds want to know :troll

Noel

 

If you are going to ground the amps to the car, you need a meter.
Test the voltage reading on the battery itself first. After you run the amp power wire to the back of the car, use your meter connected to it, and probe your proposed ground spot with the negative probe (he he.. i said probe twice) You should have almost the exact same voltage as when you tested the battery. You will be suprised at what will "work" and what is the "best" ground. In the C5, the seat bolts are nowhere near as good as the rear shelf.




[Modified by leolufse, 11:00 AM 11/17/2003]

 

You never want to run your ground all the way to the battery. You will create ground loops in doing so. To find or good ground spot you need a multimeter that will do continuity and able to zero itself. You also need a long piece of wire to make the test probe long enough to reach the rear of the car. Now attach the piece of wire to the pobe so it won't fall off. Set the meter to continuity (measure resistance ohms) and touch the other end of the wire to the other probe. Zero the meter. By seroing tthe meter it no longer reads the resistance of the piece of wire. Now attach the long probe to the negative terminal of the battery and take the other to where you are thing of grounding the amp. Touch the probe to the spot and look at the resistance. You want it to be as low as possible. I try to get a zero resistance.

Now here is something cool for you "Big 3" upgrade guys. Pick a spot to measure resistance. Before you do the upgrade. Measure from that spot and try do it from a spot that has high resistance. Write down what it is. Now do the upgrade and remeasure. If your measurement is now lower your upgrade was a success. Along those same lines if you can not find a good spot to ground try adding another ground to the chassis from the neg terminal on the battery. This will help and will help reduce noise. I do this alot when I have a car with noise. Noise troubleshooting is one of my specialties. I have spent alot of time talking about noise with Richard Clark and Larry Fredricks, formerly the top engineer for Phoenix Gold, I do not know what Larry is doing now but he is the one that taught me how to measure for a good ground and to add the ground wires on the battery.

I am not familiar with the way Leo mentioned but that does not mean it does not work....this is just the way I do it.
Hope this helps and you guys understand it all. :cheers:

 

One other thing. I do not use a screw to mount my grounds. I use either a nut and bolt provided I can get to the back side of the bolt. In most cars this is very easy. Or I use what is called a nutsert. Which is a compression nut ....I have a kit that I drill a hole stick the nutsert on the gun and put it in the hole. Pull the gun (it is like a rivet gun ) and it compresses the nutsert now giving my a threaded spot to put a bolt into. I do not like to use screws because most of the time it is put into 18ga sheet metal and always comes loose. If the screw was put into double wall then it is not so bad but I just stopped using screws and only use stainless bolts now.

 

basically, i'm doing the same thing as EatRice... testing resistance by using voltage instead of ohms. Let say at the battery the meter reads 12.5 volts. After I run the power cable to the back of the car, I stick the + probe into the wire and again measure the voltage at the battery. You have resistance in the wire, so lets say the reading this time is 12.3 volts. Now, I use the ground probe on my "proposed" grounds. If I can achieve 12.3 volts, the ground is as good as hooking to the battery itself, but w/out the possibility of ground loop or wasted power due to line loss