2001 Bullitt interference since installing aftermarket headunit

[rebel842001]

Ok so here's the deal. I took out the stick 6 disc changer headunit and installed my pioneer in dash screen that I had in my truck. I ordered a mount kit, mach 460 wiring harness kit, and a 12 to 5 volt reducer that was recommended to eliminate a pop that can be heard if you don't reduce the voltage on the amp power turn on wire.
I got all this from Crutchfield. Got all this in the other day so I worked on hooking up the wiring connector to the connector to my in dash screen. Im pretty positive ive hooked it up correctly, since this isn't my first time changing a radio. But im picking up an interference, to me it sounds like an extremely loud fuel pump sound. Only does it when the engine is running, and doesn't change with rpms of engine or the volume of the radio. I turn the radio up to about where I like it I cant hear the interference over the music and general road noise. But if im just cruising through town and turn the music down it drives me insane. Anyone have any clue what the deal is or what I need to check out to eliminate this.

 

[ttocs]

Are you using the rca outputs on the deck to feed into the mach system or are you using the speaker level outputs?

 

[rebel842001]

I hooked the speaker out from the headunit into the speaker wires on the harness kit green to green purple to purple white to white and gray to gray like any other headunit install ive done before, but ive never done any work on the mach system. I hooked the connector with the rca plugs into the sub output on the headunit. im getting good sound out of it. It actually sounds better than the stock headunit to me, sounds a lot cleaner at higher volumes. Its just at the lower volumes I can hear that damn extremely loud fuel pump sound. It only does it when the engine is running. It does not do it with the key turned back to Acc. or even turned to on with out the engine running, but soon as you crank it and the headunit boots back up there the interference is.

 

[ttocs]

Was there an extra black with a white stripped wire on the hrns labeled amp ground? If so did you ground it?

Is this in a convertible?

 

[rebel842001]

yes there was a black and white wire for amp ground from the main plug and also a amp ground one the plug with the rca cables and I wired thoses wires together. I figured the ground was running through the factory headunit from one plug to the other so they needed to be wired together in order for the amps to turn on. I can play with the sub output on the headunit and hear the subs change as I change settings so Im pretty sure the amps got to be turning on. Ive completely redone the sound system in my truck with about 2g worth of equipment from headunit to amps caps and all door speakers and subs, but this is the first ive messed with a factory system with amps and subs. So im kind of in unfamiliar territory with this headunit install

 

[ttocs]

Is the sound coming through the sub or the tweeters?

Pioneers have been known to have a noise problem if you are not carefull with their rca cables/connections after the deck has been powered up. There is a super small fuse(called a pico-fuse) that will blow if you ground/short out the rca's on the back of the deck after it has been powered up. You can test if this is the issue by simply grounding the outer shield of the rca's behind the deck.

Also still curious if it is in a convertible as the amps are mounted directly on top of the gas tank/fuel pump area and could pick up some noise but I would not know how it would be induced on a hard top.

 

[rebel842001]

no not a convertible. the bullitt is a coupe only

 

[ttocs]

missed the model in the title, I am more familiar with the 94-95s. I know on the 94-95 there is a noise condenser I think its called that is mounted on top of the coil under the hood. Its nothing more then a coil to try and shunt any noise created to the block to try and prevent it from going to other areas, look like a small battery with I think one wire going too it. Turn on the radio and see if playing/adjusting/tapping on it makes any difference in the noise.

 

[rebel842001]

2001 has coil on plug setup on the 4.6. im not sure since I haven't fooled with these newer mustangs till I got this bullitt but if I understand correctly the 94-95 have the 5.0 which still has a distributor and a single coil and I do believe I know what your talking about and I think its a capacitor, probably half inch diameter and around an inch or so long with a single wire coming out of one end. I use to work as a GM tech about 6 years ago and still then just about everything GM had was already a coil on plug set up so its been quite a few years since ive even really looked at an older engine that still had a distributor.

 

[ttocs]

right different system but I am willing to bet there is a noise condenser in there somewhere.

 

[sn95 bullitt]

Rework them grounds. On my mach rca I wired the grounds separate from the power/door speaker hatness ground. I don't know if that's your problem are not. Mine sounds fine low are high.

 

[sn95 bullitt]

Both blues go down into one on the HU

Both blacks go down into one on the power harness that says amp ground.

 

[rebel842001]

that's how I got mine the two black grounds from the rca plug connector are hooked to the one amp ground from the other connector only difference from mine to yours I put I a voltage reducer going to the blue and white amp turn on wires and the headunit remote wire. I did this because crutchfield suggested the reducer when I added the wiring kit to my cart, according to them the amp only need 5 volts to turn on not 12 and the amps will make a pop when first powered up if you put 12v to the turn on wire. Did you hook up the 4 sets of speaker wires up from the headunit connector to the harness connector and what did you plug the rca into?

 

[ttocs]

Is it coming from the woofers and the tweeters or one/other?

Just for giggles try taking the reducer out and see if that helps. Its possible that it might be just below the threshold voltage needed on the remote wire to keep the amp on well enough to make good sound. While you are back there also try grounding the outer shield of the rca's and see if that makes the noise go away. If neither of those works well its going to sound silly but trust me it works. Get a little rough with your connections/hrns's. Pull/tug/jiggle (to get technical) them and see if it makes any difference. If you have made your connections correctly you should be able to pull on them with a descent amount of force and not have them come apart or make any noise issues. If still nothing then go back to the amps in the back and do the same thing with the wires going to the amps.

 

[rebel842001]

best I can tell its coming from the rear of the pass compartment. ill go play with it sometime today and see what I can come up with

 

[ttocs]

try to isolate if its the tweeters in back or the woofers, or both.

 

[rebel842001]

Well i just pulled the headunit unplugged the rcas with the car running and radio playing. And soon as i unplugged them the noise quit, plugged them back up and no noise so figure it was not getting the good ground on the rcas. Unplugged them and used some pliers to squeeze the outer ring some to make a tighter connection. We'll see how long this works.

 

[ttocs]

unfortunately that really didn't show us much. The noise could be from the deck, it could be down-line in the amps/wiring and it isn't a loose ground shield on the rca that's a problem.

To ground the outer shield of the rca the way I am telling you to do is to just take a piece of wire and touch it too the outside shield of the rca cable(either or) and then ground the other end of the wire. If you don't want to hold both ends you can pull the rca's apart and just slide the wire between the two pieces when you plug the rca back in. I know it sound strange but I assure you with the +15 yrs of audio security installation exp that I am not setting you up for failure. If it isn't the pico fuse problem it will not make any difference. If it is you should hear the noise on one side of the rca's go away.

 

[rebel842001]

Well like i say the noise is gone now im happy but if from some reason it comes back ill get more in depth into it then.

 

[Nightmare]

Interesting. When I installed my dvd unit 5 years ago, there was nothing mentioned about a reducer from Crutchfield. Just a simple wire up the harnesses by color, plug in the rcas/harness/done........if it happens again, remove the reducer. I have seen nothing but issues when you add stuff in line like that.