Can't get rid of interference noise

keybrdcowboy1 · Oct 22, 2004

Can anyone help me out? I installed a system in a friend's 88 F150. He bought everything brand new. We are running dual amps, with a Pioneer head unit, new door speakers and he added two 6x9's to the top of his box in the back. (His F150 didn't have any rear speakers factory) I have regrounded everything several times, used several different RCA cables, and have ensured that the power and signal wires are not routed anywhere near each other. Is there anything else I can do to try and fix this problem? Could it possibly be a bad ground somewhere else in the truck not relating to the speaker install? let me know if you can please. Thanks.

1985MustangGt · Oct 23, 2004

Does the noise go with the rpms?

JokerWylde · Oct 23, 2004

When you say you've regrounded everything, you are making sure to scrape off any paint or other crap at the grounding point, right? When you say "everything", does that include regrounding the head unit itself?

keybrdcowboy1 · Oct 23, 2004

1985MustangGt said:
Does the noise go with the rpms?

Yes, I believe it does. I haven't actually ridden in it since the stuff has been installed, but if I remember correctly, I did push the accelerator down and I seem to remember the pitch going up.

keybrdcowboy1 · Oct 23, 2004

JokerWylde said:
When you say you've regrounded everything, you are making sure to scrape off any paint or other crap at the grounding point, right? When you say "everything", does that include regrounding the head unit itself?

Yes. I didn't scrape any paint off, but.... the ground for the amps is going to a distribution block, which is grounded to the bolt hole where the back seats used to be. I am using the same bolt and I'm farily certain there isn't any paint there. But barring even that, I made a test cable and I tested various spots all over the car, and none of them made a difference. And I reground the head unit to a different ground within the dash, and also used the test cable to try different grounds throughout the car. Any other ideas? Thanks guys.

saxman9801 · Oct 24, 2004

keybrdcowboy1 said:
Yes. I didn't scrape any paint off, but.... the ground for the amps is going to a distribution block, which is grounded to the bolt hole where the back seats used to be. I am using the same bolt and I'm farily certain there isn't any paint there. But barring even that, I made a test cable and I tested various spots all over the car, and none of them made a difference. And I reground the head unit to a different ground within the dash, and also used the test cable to try different grounds throughout the car. Any other ideas? Thanks guys.

You got the power wires away from the rcas what about the grounds? If the rcas are near the grounds it will do the same thing, make sure that if the rcas cross the power or ground wires they do so as a T so they do not grab noise, make sure the ground wire is secured into the amp well and not loose, same with the power wires bad connections can make the whole install sound like crap. Dan

keybrdcowboy1 · Oct 24, 2004

saxman9801 said:
You got the power wires away from the rcas what about the grounds? If the rcas are near the grounds it will do the same thing, make sure that if the rcas cross the power or ground wires they do so as a T so they do not grab noise, make sure the ground wire is secured into the amp well and not loose, same with the power wires bad connections can make the whole install sound like crap. Dan

Yes, the RCA cables are nowhere near the ground wires. Like I said, I have redone everything several times, so they should have good connections. Thanks.

ChingonStang · Oct 24, 2004

The next thing I would suggest is try to find out if its maybe one of the amps by running each by itself to see if maybe one of them is causing the problem. Also just run the radio by itself to see if the problems lies there....hope that helps.

draenoor · Oct 25, 2004

I have a similar problem in my 01 stang.. I think it's in my HU, maybe you should check wires there. I have my fronts running on an external amp, but my rears are running on the HU amp. When I unplug the front speakers' amp, the noise remains in the rears. Still tryin to figure out how to fix it though...

Also, I notice that the noise comes and goes, literally based on how hard i accelerate or brake. If i brake hard, the noise becomes more prominent, then when I accelerate, it fades. I get the feeling that's caused by wires moving closer and further away from eachother. Anyone have thoughts?

keybrdcowboy1 · Oct 25, 2004

ChingonStang said:
The next thing I would suggest is try to find out if its maybe one of the amps by running each by itself to see if maybe one of them is causing the problem. Also just run the radio by itself to see if the problems lies there....hope that helps.

Well, at the time I did all this, the amp powering the subs wasn't even connected. So I know it's not that one. Before I ever hooked up any amps, I tested the radio and the two front speakers, and they played fine with no problems.... Course, now that I think about it, I didn't have the vehicle on at the time, so that's not a guarentee. To test the wires coming out of the head unit, I had it all out and I wiggled all the wires, and it never made a difference. So I don't think it's there. I seem to remember something I read a long time ago about getting some kind of something to make the alternator whine go away. But I can't for the life of me think what it was. If anyone can offer any more help, that would be great. Thanks.

keybrdcowboy1 · Oct 25, 2004

draenoor said:
I have a similar problem in my 01 stang.. I think it's in my HU, maybe you should check wires there. I have my fronts running on an external amp, but my rears are running on the HU amp. When I unplug the front speakers' amp, the noise remains in the rears. Still tryin to figure out how to fix it though...

Also, I notice that the noise comes and goes, literally based on how hard i accelerate or brake. If i brake hard, the noise becomes more prominent, then when I accelerate, it fades. I get the feeling that's caused by wires moving closer and further away from eachother. Anyone have thoughts?

On my own car, I had a slight whine occuring. When I took the head unit out and had all the wires laying out, I redid all the connections and made sure that none of the wires were intertwined between each other. That made mine go away. I think I had one or two of my speaker wires going in between my rca cables....good luck to you.

saxman9801 · Oct 25, 2004

keybrdcowboy1 said:
Well, at the time I did all this, the amp powering the subs wasn't even connected. So I know it's not that one. Before I ever hooked up any amps, I tested the radio and the two front speakers, and they played fine with no problems.... Course, now that I think about it, I didn't have the vehicle on at the time, so that's not a guarentee. To test the wires coming out of the head unit, I had it all out and I wiggled all the wires, and it never made a difference. So I don't think it's there. I seem to remember something I read a long time ago about getting some kind of something to make the alternator whine go away. But I can't for the life of me think what it was. If anyone can offer any more help, that would be great. Thanks.

You can get a ground loop isolator which will kill lots of noise and see if that helps, sometimes a bad altenator will create some noise in your system, give one a shot Dan

keybrdcowboy1 · Oct 26, 2004

saxman9801 said:
You can get a ground loop isolator which will kill lots of noise and see if that helps, sometimes a bad altenator will create some noise in your system, give one a shot Dan

Yeah, that's what I was trying to think of. Thanks a lot. I think we will give that a try. And I just connect this between my head unit and the amp?

saxman9801 · Oct 26, 2004

keybrdcowboy1 said:
Yeah, that's what I was trying to think of. Thanks a lot. I think we will give that a try. And I just connect this between my head unit and the amp?

Yup plug rcas into it the unit and the unit into the amp, make sure you do it at the amp side or else you defeat the purpose of the isolator. Good Luck Dan

ChingonStang · Oct 26, 2004

I remember on my dad's surburban after he got a new head unit and amplifiers put in, his system whined. About a week later...the alternator literally fell apart. When we replaced it, there were small pieces coming out of the old dead alternator. After putting in the new one, everything was fine.

keybrdcowboy1 · Oct 29, 2004

Okay, well I bought a ground loop isolator from RadioShack, and that didn't do squat. Still had the same terrible noise. Does anyone have any other ideas? I did confirm that it is alternator whine. Pitch goes up when you hit the gas. The alternator looks to have been replaced sometime in the last 2 or 3 years. Also, I don't know if it makes a difference, but the amp makes a loud noise through the speakers anytime you turn on or off the head unit. Can anyone offer any other help? Thanks.

JokerWylde · Oct 29, 2004

Just another thought...are the amps both grounded to the same spot, or do they each have their own grounding point?

keybrdcowboy1 · Oct 29, 2004

JokerWylde said:
Just another thought...are the amps both grounded to the same spot, or do they each have their own grounding point?

Both the amps go to a ground distribution block, which is then grounded to the frame of the truck. They enter the distribution block through different ports if you will......

saxman9801 · Oct 29, 2004

Where are all the wires ran? I know you have tried different sets of rcas, but have you ran them in the same spot, Couple of things to check. Where are the amps mounted are the mounted flat and nothing is pushing down or twisting the amp body around, Make sure nothing is pinching the rca's no screws through them anything like that, the rcas are picking up something in the truck possibily like a fuel pump relay or a high current wire, take a pair of rca's you know are 100% good and plug them into the headunit and plug them into the amp leaving them draped across the center of the truck, If that works then you know somewhere along the way the rcas are the problem, what makes engine whine is either rcas picking up interference or bad grounds. I know you said you tried new grounds but try scraping the paint off real good and then grounding the units there. How long are the rca's and where did you leave the excess? Good luck and let us know how it goes Dan

keybrdcowboy1 · Oct 29, 2004

saxman9801 said:
Where are all the wires ran? I know you have tried different sets of rcas, but have you ran them in the same spot, Couple of things to check. Where are the amps mounted are the mounted flat and nothing is pushing down or twisting the amp body around, Make sure nothing is pinching the rca's no screws through them anything like that, the rcas are picking up something in the truck possibily like a fuel pump relay or a high current wire, take a pair of rca's you know are 100% good and plug them into the headunit and plug them into the amp leaving them draped across the center of the truck, If that works then you know somewhere along the way the rcas are the problem, what makes engine whine is either rcas picking up interference or bad grounds. I know you said you tried new grounds but try scraping the paint off real good and then grounding the units there. How long are the rca's and where did you leave the excess? Good luck and let us know how it goes Dan

Well, the RCA's we are using came in a Rockford Fosgate wiring kit, so they should be some decent quality wires. They are running along the driver side of the car, while the power is running along the passenger side. So they should be plenty far apart. When testing with the other RCA cables, those were just draped across the center of the truck over the seats. So the location shouldn't be a problem. The amps are mounted to a amp rack in between the subs. Screwed up there. There should be plenty of room for the wires underneath the amp. I hate having something like this beat me. Anyone have any other ideas? Anyone know how to use a voltmeter to test the RCA inputs and stuff on the amps? I was reading about that today. I'm going to see if the antenna is causing the interference, but more than likely its not. Getting desperate here. Thanks so far though.

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