checking ground wires with meter?
 

So i'm suspecting the grounds running to my amp and cap aren't the greatest as i get a decent amount of headlight dimming when i turn the stereo up to a decent volume and I am running less then 1,000 rms. my battery could probably use replacing soon but i would like to check through my grounds.

I currently have the big 3 done with 4 gauge, I'm running 4gauge back to the cap then to amp. The amp and cap are both grounded to the seatbelt bolts under the back seat. I scraped off the paint and such from around the bolts I didn't put a terminal on the wire though, It's just a bunch of wire wrapped around the bolt then held down by a nut.



So they main part of why I am posting is because I know there is a wait to check the grounds with a multimeter but I am unsure of how to go about doing this. If somebody could post how, that would be awesome it would be a bit better if you could post it in simple english to somebody who hasn't used the multimeter much :)

Also when i check the grounds with the meter should i have the car running with the system going?

nevermind i got it figured it, rather easy :) now i just have to actually go check them lol

Well, I've got some questions for you.

1. What size is your power and ground wires for your amp?
2. Where is your power wire run from? The battery itself or the fuse box?
3. How long would you say your ground wire is?
4. What type of wire are you using for your power/ground? CCA or copper?
5. Why did you install a cap?
6. Why did you choose to ground to the seat belt bolt?

You always want your power and ground wire to be the same size as each other and preferrably the largest size your amp will accept. Same for the Big 3, you want that wire to be as large or larger than the amp power/ground wires.

It's generally a good idea to keep your ground wire as short as possible. Seat belt bolts are a common place alot of DIY'ers ground to but it's not always a good place. Best way to find a good ground spot is to measure the resistance in ohms using a dmm, connect one lead of your meter to the front battery negative post using a long enough wire and with the other lead, touch it to potential ground locations. You want the measurement to be as close to 0 as possible and no more than 1 ohm.

I would highly suggest that you terminate the end of your ground wire with a nicely crimped or soldered ring terminal, it's just a cleaner more efficient end to a means. A spot that has done me well over the years is the shock tower bolt. Measure the resistance there and compare it to the reading you get at the seat belt bolt and see which one yields a better measurement and use that one.

1. 4 gauge wire all around
2. battery
3. 18 inches
4. copper
5. i don't know just did :)
6. sounded like a decent idea

I took readings with the DMM on a 200 ohm scale, all grounds read .04, also when i make contact to both points of the DMM by themself they read .04 so i think my grounds are good. I set my amp with the DMM like you suggested to.

Take readings with dmm set at 2 ohms, or 20 if yours doesn't go that low. So what amp are you running? Seems to me you aren't measuring right, but either way, caps are a waste of time, space and energy if you're putting it in due to lights dimming. I could go into a big diatribe about that but if you do a search on the forum i'm sure you'll find out why. The lights are dimming because your alt can't supply the power needed so the power is pulled from the battery. Adding a cap only adds another current draw. Seat belt grounds are usually "dirty" grounds so I'd say ditch that location and go with a shock tower bolt. And have your battery tested, that can be a problem too. How do you know your wire is copper? Cause of the color? Don't let that fool you, most CCA wire is copper in color too. What wire are you using, as in brand?

I'm using a alpine class d mono block I don't have the model number handy at the moment. I'll try deleting the cap and see how that goes. My battery has a decent chance of being on it's way out it looks kinda old I've only had the car for close to a year now. The wire i bought off the spool from the local radio shack