The Headunit works w/o negative wire connected!! What's going on?

jasonsjwou · 07-20-2007, 10:38 PM

I had an alternator noise problem which I fixed with a better RCA cable. A monster's twisted pair RCA solved this problem.

But I found something weird. I disconnected the negative wire from my head unit, and it was still working. Then I reconnected the negative wire while the headunit was turned on, and it didn't make any difference.

What sort of problem am I having here?

TruckinMP3 · 07-20-2007, 10:49 PM

it must be grounded by another connection. Is the radio is still mounted when you found this?

jasonsjwou · 07-20-2007, 11:23 PM

This is what I know.

1. There is a noise, sounding like a static trickling noise, even when the engine is off. Whining noise is completely gone, but there is the static trickling noise even with the engine off.

2. I disconnected RCA cables from the headunit, and the noise is gone.

3. I am using a wire harness, with all the factory speaker wires attached.

4. I am using remote amp turn on from the Head unit. May be I should connect this to ACC+?

5. I draw 12V power through the wire harness. I tried to do this directly from the battery, and it didn't do anything

6. If I "pause" the head unit while it's playing the CD, the noise goes away.

I'll post more as I find more about it.

jasonsjwou · 07-20-2007, 11:24 PM

Quote: Originally Posted by TruckinMP3

it must be grounded by another connection. Is the radio is still mounted when you found this?

Well. yes... I had to connect everything to turn on and listen to the head unit... that's when I found this.

BrokenBC · 07-20-2007, 11:42 PM

The headunit most likely is grounded to the chassis and the chassis is probably screwed into something that is connected to ground.

the sound... how loud is it? your running aftermarket amps? one guess is that the sound your hearing is just the static that every deck makes... there is no such thing as silence. now depending on how your amps are set up though you might be able to turn down your gain on the amp which might help lower that static you hear, you'd just have to turn your deck up higher to get the same volume out.

the fact that you disconnect the RCA's from the deck though and have no noise then makes me think that whatever it is its comming out of the deck. Your power source/ ACC should not change any of this.

jasonsjwou · 07-21-2007, 12:01 AM

Is it normal / possible / OK to have the headunit being able to run without its ground wire connected? will it blow something up later?

Felix509 · 07-21-2007, 12:04 AM

bolting the deck in is a pretty good ground on some cars, as it is probably to the chassis through all the metal bracing... '

Depending on the car a deck could definably run via just being bolted in as the ground..

Have you checked that your RCA cables have no cuts where the wire could be grounding to the chassis??

best of luck with your install. .

rutger1413 · 07-21-2007, 12:18 AM

Try a set of RCA ground loop isolators, this might work. Also double check the ground on your amp(s). You may still want to ground the deck b/c it cant hurt if you double ground it.

jasonsjwou · 07-21-2007, 02:32 AM

I think I solved the noise problem. I had the amplifier gain bit too high, so I adjusted the system again. I lowered amplifier gain, raise the volume of the HU upto about 80% (at this point the sound is not all that big) and I raised amplifier gain so that it is just a tad louder than what I can tolerate in terms of loudness.

When I did this, the trickling noise disappeared under the noise floor.

Thanks BrokenBC, your suggestion worked.

BrokenBC · 07-21-2007, 01:56 PM

glad I could help

pancit175 · 07-21-2007, 08:42 PM

Just to chime in a day late, but the antenna could also act as a ground, but from what I've been told before, its not recommended to keep it that way. I know that its horrible to say this an not explain why but I can't remember everything or word it right. Something along the lines of the antenna ground is not intended for current flow. The only thing I can back this up with is that you always want to have the ground cable to be as short as possible and if you use the antenna as a ground it is more probable to accept ground noise because of the long stretch the antenna cable is. There is more to it, but I'm having a major brain fart.

jasonsjwou · 07-21-2007, 09:16 PM

I tried to take the antenna out, and that wasn't it. I think it might be grounded through the RCA cable back to the amp.

pancit175 · 07-21-2007, 09:47 PM

thats also possible too. But thats even worse to let happen for too long. because that ground in the RCA cable is probably only at best 20 gauge. I've seen that let happen for too long before causeing the ground wire in the RCAs to cause a break in the line which may also cause the noise you are experiancing.

If you'd like to attempt to continue to troubleshoot this problem, I would also suggest to change out your RCA cables, or upgrade the quality of your RCAs if they are not of decent quality.

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