In article gers.com,
"Duncan A. McRae" wrote:

Maybe you folks can help me out with a problem I'm having with a
recently-installed system.

BACKGROUND
Quite a while ago, I went to the Future Shop in Oakville and picked up a
Clarion stereo, MTX 4244 amp, MTX 12" sub (boxed) and a pair of Infinity
5.x" speakers for my doors. This was all installed in an old BMW 525i, then
transferred to my Acura CL3.0 with no problems (the speakers weren't
transferred because the Acura uses 6" speakers up front). In March, the
Clarion stereo was stolen. I had the bodyshop replace the stock (Bose)
system which I'd kept, and all was fine (though not as clear and powerful as
the old system, obviously). Most importantly, there was no alternator
noise, nor any other intrusion into my listening pleasure, save the quality
of the system.

LAST WEEK
I took the Acura back to Future Shop and picked up a new stereo, a Panasonic
CQ-DF583. I also had the speakers installed by using plastic cuffs (anchor
speaker to cuff, anchor cuff to mount). It appeared that the original
installer had cut some corners; the speaker wire and power wire were run
down the same (driver's) side of the car, and there was only one set of
RCA's going back to the amp (the fronts, rears and sub were ALL being run
off a single channel). When we turned the deck on, there was a high-pitched
whining, which changes with engine speed. Based on conversation with the
installers and research in this group/on the 'net, I'm pretty sure it's
alternator noise.

TODAY
I took the CL back again today to get a second RCA strung to the back, and
to upgrade the deck to a CQ-DF783. The only real difference is that it
boasts two pair of pre-outs and a separate dongle for the sub. Anyway, the
speaker wires were strung down the passenger side (fronts & sub get the
wires to&from the amp, back speakers run straight off the deck), the new
radio was installed, and the whine from the system is damned near deafening.
I noticed that it decreased on the drive home. It was raining heavily,
which might have improved the bad-ground situation, if that's the problem.

I just went to the vehicle to check things out, and here's what I found:
- the amp is grounded to the d/s wheel-well. The paint was not (as far as
I can see) sanded away first, but a metal (piercing) screw was used.
- the grommet is separated from the head of the screw by a stack of
washers, likely to keep the screw from going so far through the housing that
it pierces my tire.
- the cord is perhaps 24" long, spliced half-way (the amp was once mounted
to the BMW, and so the wire only had to go a few inches to ground).
- I pulled the deck and checked the aerial; it's snuggly seated in the deck
- I cannot check the connections in the wiring; they've been wrapped in
electical tape.
- I actually get TWO noises from the system; the first when I turn the key
to the "accessories" stage, and then the alternator whine is added when I
turn it on.
- Of the two, the first (accessories-only stage) is louder.

I spoke with the install manager, and he suggests that it could be caused by
a bad ground in any other system in the car. I didn't understand what that
had to do with anything, since there was no noise prior to their
installation last week. The installation this week comprised simply of
pulling the old stereo out and sliding the new one in; that shouldn't have
been a factor. They offerred to check it out and cap the expense to me at
$200. I don't feel happy paying ANYTHING, let alone $200, to fix a problem
that didn't exist before they did the installation last Saturday.

I've already called the Future Shop and asked that a manager get involved to
help sort this out; I'm prepared to let the dude have my car all day (a
large inconvenience in itself) but I DON'T see that I should have to pay for
it.

Is there anything I can do before next weekend to rule out other systems?
I've seen on the 'net that I could
- replace my spark-plug wires, which seems a little odd, and
- install a capacitor between my alternator and... something.

Is either step reasonable, inexpensive, and an easy DIY job? I'm not afraid
to pull wires & such (I've built twenty or thirty computers, and tinker with
my remaining 9 regularly), but I'm no mechanic.

Thanks folks;
Duncan


Make sure that the amp's negative terminal, and nothing else, is very
well grounded. The RCA cables should be grounded only from inside the
head unit, nowhere else. The speaker cables should not be grounded
except for maybe inside the amplifier.

Remove the RCA cables and check the voltage on the chassis of the head
unit. It should be less than 0.1 volts. More voltage (or the HU not
turning on) means it has a bad ground.

Connect a handheld amplifier (like Radio Shack's) to the RCA cables on
the HU, with no other RCA cables connected, to see if there's noise
without a ground loop.