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And when I measure the resistance to check for good grounds, I get around 3.9 Ohms on the 200 scale. When something is turned on (lights, door opened, etc), the ohm reading goes up really high. I get readings from 15 ohms to 25 ohms. This is probably what's causing my alternator whining.
I started to do this to track down alternator whine problems.
The only place I get a good ground (.4 ohm reading) is the frame rail grounds near the engine bay.
I have verified my multimeter (please check settings) as good (0.1 ohms)
When I connect to a supposed ground (lighter, center console) and the battery terminal (through a 10 gauge wire to the back of the car) I get an increased ohm reading which should be close to 0 for a good ground.
If I turn on my headlights or high beams, the reading jumps up to 25 ohms or greater. (See added video)
I dont know. I added a video to the first post.
Last edited by freddyvette; 06-27-2016 at 08:45 PM.
It isn't negative resistance (no such thing), when you turn stuff on/off it slightly changes the potential (voltage) on the circuit you're on and your meter is reacting to that change. You may even have a very small amount of current getting into the meter.
These cars are very sensitive to electrical issues, I put LED turn signal bulbs in my '07, one of them melted and for a while it caused my entire dashboard to blink whenever I put on my left turn signal due to a reversed current flow.
You can try running a new ground wire that connects all of your new equipment to a factory ground bolt, but you may also need a filter like this one on the supply side of your HU and interface adapter.
It's hard to tell from the video, but if you have an aftermarket amp you can add some GLI's also.
It isn't negative resistance (no such thing), when you turn stuff on/off it slightly changes the potential (voltage) on the circuit you're on and your meter is reacting to that change. You may even have a very small amount of current getting into the meter. Yes, I realized halfway through making the post that the terminals were reversed. But the observation still remains valid, when an accessory is turned on, the absolute value of the resistance to ground increases by quite a bit
These cars are very sensitive to electrical issues, I put LED turn signal bulbs in my '07, one of them melted and for a while it caused my entire dashboard to blink whenever I put on my left turn signal due to a reversed current flow. My issue is just an alternator whine. Although, I do have a problem with parasitic drain and I believe it may be related. Trying to get to the bottom of it
You can try running a new ground wire that connects all of your new equipment to a factory ground bolt, but you may also need a filter like this one on the supply side of your HU and interface adapter.
It's hard to tell from the video, but if you have an aftermarket amp you can add some GLI's also.I dont have an aftermarket amp. I am connecting the stereo through to the factory amp, which does give some gain issues but I don't really feel like spending 1k+ on a new speaker and amp.
I replied in red. Do you have any suggestions as to why ALL of my grounds to the same thing? I just tested the frame rail I mentioned earlier, and it does the same thing. I was under the impression that the ground should remain close to 0 ohms regardless of what's turned on. Am I wrong?
If A is your radio plug, and G is the (-) battery terminal, the physical resistance from A-G does not change.
Your meter is measuring resistance from A to G, which goes through several connectors, wires, the frame, etc...
If the lights are grounded at point D, when they are turned on there will be a small change in potential from A to D, and your meter is detecting that change. The resistance isn't changing, the voltage across your meter leads is.
Odds are you have a bad connection(s) somewhere in the grounding circuits of your car, which is causing your issue. Cleaning and/or tightening G104 and the battery ground cable may help. If not, the power line filter I linked to in my previous post has a good chance of hiding the issue.
If A is your radio plug, and G is the (-) battery terminal, the physical resistance from A-G does not change.
Your meter is measuring resistance from A to G, which goes through several connectors, wires, the frame, etc...
If the lights are grounded at point D, when they are turned on there will be a small change in potential from A to D, and your meter is detecting that change. The resistance isn't changing, the voltage across your meter leads is.
Odds are you have a bad connection(s) somewhere in the grounding circuits of your car, which is causing your issue. Cleaning and/or tightening G104 and the battery ground cable may help. If not, the power line filter I linked to in my previous post has a good chance of hiding the issue.
Hi Mark,
Thanks for your help so far. What I've done is cleaned G104, Underhood Fuse Block, and both battery terminals.
It hasn't affected the behavior.
I understand what you're saying with the power line filter, and I might try that in the future, but do you know if there is any way to track down where the bad connection is? Maybe by pulling fuses? I'm really OCD about this kind of thing
Trial and error with a meter is about the only way to find it unless you have one circuit that is obviously worse than the others, if you do look for the ground bolt it's attached to.
I'm at the point now that I always install a power line filter with any new HU install. It doesn't affect the audio at all and clears up many issues before you even have them.
Trial and error with a meter is about the only way to find it unless you have one circuit that is obviously worse than the others, if you do look for the ground bolt it's attached to.
I'm at the point now that I always install a power line filter with any new HU install. It doesn't affect the audio at all and clears up many issues before you even have them.
I'm having both a static white noise (hiss, fuzz) in ACC mode, as well as a speaker alternator whine with the engine ON. I've tried grounding to multiple places. I just don't know how to trouble shoot the problem.
Mine was an older Vette (2000), from a dry climate and maintained very well, but had many minor electrical gremlins, though no trouble codes. What worked for me was:
- clean all factory ground points, battery connections
- unplug, clean, and replug all the major wiring harness connections in the engine bay. There were several very corroded pins.
- Add several 'extra' ground straps: Alt to frame, starter to frame, Batt (-) to frame
- Unplug, clean, and replug the major (+) connections to fuse box and starter
YMMV. I had minor alt whine, starter slow to engage, etc. All cleaned up with the above.
Mine was an older Vette (2000), from a dry climate and maintained very well, but had many minor electrical gremlins, though no trouble codes. What worked for me was:
- clean all factory ground points, battery connections
- unplug, clean, and replug all the major wiring harness connections in the engine bay. There were several very corroded pins.
- Add several 'extra' ground straps: Alt to frame, starter to frame, Batt (-) to frame
- Unplug, clean, and replug the major (+) connections to fuse box and starter
YMMV. I had minor alt whine, starter slow to engage, etc. All cleaned up with the above.
Hi Acroy. Thanks for the suggestions. What did you do to clean up the wiring harness connections? Some of those plugs are very complicated.
Also, would you recommend grounding the alternator to the front left rail ground? Say... 8 gauge wire?
Mine was an older Vette (2000), from a dry climate and maintained very well, but had many minor electrical gremlins, though no trouble codes. What worked for me was:
- clean all factory ground points, battery connections
- unplug, clean, and replug all the major wiring harness connections in the engine bay. There were several very corroded pins.
- Add several 'extra' ground straps: Alt to frame, starter to frame, Batt (-) to frame
- Unplug, clean, and replug the major (+) connections to fuse box and starter
YMMV. I had minor alt whine, starter slow to engage, etc. All cleaned up with the above.
Cleaning all of the factory grounds and doing the 'big 3' should help a lot.
Originally Posted by freddyvette
Hi Acroy. Thanks for the suggestions. What did you do to clean up the wiring harness connections? Some of those plugs are very complicated.
Also, would you recommend grounding the alternator to the front left rail ground? Say... 8 gauge wire?
This thread is for C5, but it has a lot of good info in it.
The alternator is attached to the engine, so a new engine block to frame ground (part of the big 3) should be enough.
I spent all day looking through the engine bay and I really didn't notice any corrosion.
I wanted to go over my plan for the DIY Big 3:
-Large gauge wire from Alternator hot lead to hot post on fuse box (battery in back)
-Large gauge wire from frame to passenger cylinder head
-Large gauge wire from alternator mounting bolt to driver side frame
Hi Acroy. Thanks for the suggestions. What did you do to clean up the wiring harness connections? Some of those plugs are very complicated.
Also, would you recommend grounding the alternator to the front left rail ground? Say... 8 gauge wire?
As I recall I used a green scouring pad and patience
The female side had corrosion on it as well. i used small screwdriver to clean it up.
Once all clean I like to put a tiny amount of silicone based lube or wd40 on the connections. The lube is not a conductor but will slow/stop future corrosion. Iv'e had really good luck with this..
For ground wire I purchased a 25ft roll of 8g wire from Amazon (I do this to all the cars) and nice crimp-on copper eyelets. Yes ground strap directly from alt to front left rail. It should not be necessary but it's easy and guarantees the alternator ground is perfect. It may be overkill but after fighting oddball electrical issues on several cars, I've gotten in the habit of grounding the heck out of everything.
06-27-2016, 06:05 PM
C6 Z06 High Ohms reading from battery to ground locations
Cleaning all of the factory grounds and doing the 'big 3' should help a lot.