Alternator whine has me stumped...

[SC4 10+ year member]

Alright, here goes...

Car: 1992 sc400

Before I got the car an audio "installer" removed the factory amp and added a memphis pr100.2 and two pioneer speakers in the rear deck, all hooked up to the stock naka head unit.

The headunit stopped working, replaced with pioneer head unit

the stock remote wouldnt turn the headunit on so i used a switched line instead, headunit turns on and plays, all is well

I exchange the original 8 gauge power wire with 4 gauge, new anl fuse, distribution block, another amp, and a sub. everything is now hooked up and power up fine but the whine starts.....

I dealt with it for a while doing some reasearch trying to learn so i could make an educated guess at what it was.

(Power and rcas ran separate)

First thing was the amps grounding location, found new, better, tighter ground for the amps (both amps running to one ground) turn on car, whine.

Next was to remove the second amp and distribution block, everything back to the way it was other than power wire and fuse, still the whine persisted

I then grounded the rcas on my headunit, nothing

I swapped my rcas for a friends that are proven to be working fine, nothing

I swapped his headunit to my car, nothing

I put the memphis 100.2 in his car with his electrical/hu/rcas and ran speaker wire to my speakers and there was no whine so it isnt the amp settings or a faulty amp in general

At that point we were almost positive it was the stock harness somehow creating the noise so we wire the headunit pos and neg directly to the battery, nothing

We then thought maybe a bad battery ground, so what did we do? removed stock ground sanded to bare metal replaced stock ground, slightly quieter noise but still definitely noticeable

As a final effort after about 8 hours of tinkering with everything we call it a day, I get a noise isolator to mask the problem so the system would at least be enjoyable, hook it up before the amp.......NOTHING.

My buddy and I are completely at a loss of where to go from here any help would be GREATLY appreciated...

Thanks in advance

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[Z1NONLY 10+ year member]

Seems like good trouble-shooting thus far.

My next step would be to run RCA's from my HU in the problem car to an amp in another car to see if the noise is happening before the amp.

If an amp in another car has noise when connected to the deck in your problem car, you can focus on the HU. If there is no noise from the amp in your "test" car, then the amp in your problem car and it's power sources, ground(s) and connections need further attention.

One other thing to consider is a possible "device" in your car that is causing noise. I had some trouble with noise and traced it back to an aftermmarket GPS unit I have hard-wired into the car. (My short term solution was to just turn off the GPS when not in use.) But there could be any number of devices that could induce noise into a system just by being connected to or near the power sources or grounds for your audio equipment.

Try turning everything off that doesn't need to be on and see if the noise stops. (GPS, Radar detector, Ipod power adapter, cel phone charger etc)

 

[sexy 10+ year member]

I have not had this type of thing happen to me but I have heard of fuel pumps with a loose ground causing a whine to resonate through the amp. There are a few more small motors in and around the engine bay that could do the same to your audio system if they were creating some ac back feed. All that said I would still be trying some more ground points and grounding more RCAs. Good luck.

 

[sacsking916 5,000+ posts]

cliffs?

 

[Z1NONLY 10+ year member]

Alternator whine coming through system.

All components tested in another vehicle and work without noise.

Connected HU directly to battery and still get noise.

Owner stumped.

 

[SC4 10+ year member]

Alright, thanks for the advice

What would cause the noise isolator not to work? This makes me think the amp/amp wiring is the issue, but when the rcas aren't connected I get no whine

 

[Z1NONLY 10+ year member]

The amp is most likely amplifying some noise it's getting from the the RCA's. That noise could be coming from the HU or getting picked up by the RCA's between the HU and amp. If you can, disconnect the RCA's from the HU and connect an ipod to those RCA cables through an adapter. (probably 5-10 bucks at Radio Shack)

Also, try to leave the RCA's routed the same way for this test. We want to see if the noise is due to the RCA running close to a "noise source" or if the HU is putting noise into the RCA's. (and the RCA's are just doing their job by getting everything that's put in one end to the other end.)

If you get noise with the ipod, try running the RCA's through a different route. If there is no noise, check the HU's power and ground connections. First try different grounding points. If that doesn't work, try running a power cable straight to the car battery just for the radio.

 

[SC4 10+ year member]

The amp is most likely amplifying some noise it's getting from the the RCA's. That noise could be coming from the HU or getting picked up by the RCA's between the HU and amp. If you can, disconnect the RCA's from the HU and connect an ipod to those RCA cables through an adapter. (probably 5-10 bucks at Radio Shack)
Also, try to leave the RCA's routed the same way for this test. We want to see if the noise is due to the RCA running close to a "noise source" or if the HU is putting noise into the RCA's. (and the RCA's are just doing their job by getting everything that's put in one end to the other end.)

If you get noise with the ipod, try running the RCA's through a different route. If there is no noise, check the HU's power and ground connections. First try different grounding points. If that doesn't work, try running a power cable straight to the car battery just for the radio.

When we tried the alternate hu we also ran his rcas outside of the car to the trunk so it has to be coming from the hu, gonna switch out the ground tonight, currently my ground is connected to a stock ground for some odd reason it is yellow but it does ground the hu.

The yellow cable comes from in the dash somewhere, couldnt locate it unless dash was completely removed, it almost looks like it was put there specifically for a grounding point it is on a bracket that the dash screws into, so until i grounded my hu it was unused just screwed into the small metal piece.

 

[SC4 10+ year member]

alright new grounding location on the chassis still whines

ran power wire from battery still whines

installed loop isolater behind headunit loop is gone but so is all enjoyable audio...

still flabbergasted