Random engine noise in subs!?

[Drifterboy3]

So I mounted my amp and subs a few weeks ago have been sounding awesome. Last week I unhooked the subs for more trunk space. Yesterday went to put them back in. The car was running but the subs were turned off at the head unit. When plugging in the +wire into the amp it sparked, and the subs hit. Now with the engine running I getting a pulsing engine sound in the subs. I checked the subs and I know they are not blown. And I know the amp is not in protection mode. Also the problem only happens when the RCA jacks are plugged into the amp. Please help !?!?

 

[mike49504]

Sounds like you have a broken rca shield ground..

What kind of head unit do you have??

 

[ODougbo]

The sound may have been there before and you didn't notice it.

Did you move any wires around? Car setups can be very "noisy" but often easy to fix. Try moving wires around, do the easy stuff first.

 

[Drifterboy3]

Pioneer, how would I fix a broken shield? And I never heard the sound before and you mean move the wires around like reroute them!

 

[mike49504]

if its a pioneer you most likely have a blown fuse for the RCA ground shiels..


If you have a multi meter set it to ohms place one place 1 probe on the outer shield of the rca on the head unit and the other probe anywhere on the caes of the head unit do you get a reading??

 

[ODougbo]

E.g. I made a compact amp box for son’s Toyota and installed it, it was the noisy noisiest thing I ever heard, like an airplane engine. I took it back out, moved a few things around, it went away, completely (not even sure what I even did).

Don’t overreact by pulling every thing out, gently move power, RCAs and speakers wires around, obviously crossing over is not good.

Did you run the power wire and the RCA line on the “same side”, or together?

 

[Drifterboy3]

Yes my power wire and RCAs are run next to each other. And same in my cousins car. And I have not had the problem until the spark. Also I'll check that in the morning. It's about 3 where I am now. So should I get a reading? If so what?

 

[ODougbo]

I don't know about other folks, I'm never going to run the power wires and RCA on the same side again, too risky.

 

[Drifterboy3]

What is risky

 

[mike49504]

If you saw a spark you more then likely have an open shield ground..

If you set your meter to ohms and do the test you should get a reading near 0 ohms if you dont get a reading at all then we will go from thier

 

[ODougbo]

You may have a fuse issue as Mike is suggesting.
Well next time….run power the power wire separate from the RCAs; not that much harder and less change of picking up engine noise(s).

 

[sofaspud]

Two things I think should be taken away from this experience:
1) car audio isn't unlike a home amp - keep line level signals away from power leads
2) make amp connections with the engine off and the battery disconnected

 

[ODougbo]

Have you gone to Car Alarm, Car Stereo, Mobile Video, and Cruise Control Info for Installers

it's one of the top "car stereo" websites.

 

[Drifterboy3]

well ya I was getting a resistance of 1 so I believe I am screwed! However I have three sets of RCAs on the back of the hu. So two questions
Are all RCAs grounded through the same fuse?
And could I use a different set of RCAs?

 

[mike49504]

If you getting a reading of 1 ohm from the rca shield ground to the case of the head unit then thats fine and is a good sign that the head unit is still working like it should..


Set your meter to dc voltage uplug the rca's and the speaker wires to your amp and stick your black probe in the negative speaker terminal and the red in the positive speaker terminal ..

What is the reading you get on that test??

 

[m4ick]

What does the meter show with the probes not touching anything? Some meters show 1 when open. I've never seen anything other than 0 ohms or open.

 

[Drifterboy3]

With the probes open I get 1ohm. When I touch to each other it drops to one

 

[mike49504]

sounds like your head unit is fine..


Set the meter to DC voltage and unplug your Rca jacks and speaker wires from the amp ..

Is there any DC voltage on either of the channels of your amp??

Place black probe on speakers negative terminal and red on speakers positive terminal

 

[bwilliams]

Perhaps the problem is not in the audio section, but in the car itself. Try disconnecting the alternator to see if you are getting RFI from it. If not, it may be coming from the ignition system. If your ignition wires are five years old or older, this could be the cause. Same with spark plugs. Find the cause of the noise before rewiring your car.

 

[Perry Babin]

RCA Shield Repair