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924RACR

I think I've finally isolated the problem with substantial whine from the engine in my stereo (in my '82 931) - engine off, stereo sounds excellent, but with the engine running I get awful whining. I've tried a number of things expecting to have issues with grounds (have a ground loop isolator, came with my amp install kit thankfully), and power etc leads are now clear of the ignition wires, but the whine remains.

Why I think it's the alternator is that I was driving home after work yesterday in the crappy rain, and as I went through a substantial puddle that splashed the engine well - the whine went away briefly! I anticipate this was due to the alternator belt slipping from the water; naturally the engine didn't cut out of course.

So that leaves me wondering about the sources and possible solutions - anyone?
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Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

DOCO · Posted: Wed Apr 15, 2009 11:39 pm Post subject:

hi vaughn biggest problem with whine caused by alt. or from ignition is that you need a noise suppresor(condenser,capasiter) in the system.usually its attached to coil or to distrbutor externally.not the condenser for the points.if you have put metal cored sparkplug wires on the car can also cause this(high performance wires).a condensor can be added in parralel to coil or alt.sorry for the spelling dave (Doc O)
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Rasta Monsta · Joined: 12 Jul 2006 Posts: 11732 Location: PacNW

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924RACR · Posted: Thu Apr 16, 2009 1:44 am Post subject:

Well, I did get back into the minivan when it snowed last week...

Amusingly enough, car has good (recently new) stock wires, no aftermarket ones!

Have a ferrite core choke I'm gonna try slapping on the alt wire... just to see...
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Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

!tom · Posted: Thu Apr 16, 2009 2:21 am Post subject:

Your rectifier could be giving you early signs of an impending failure.
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huckster · Joined: 22 Dec 2006 Posts: 115 Location: Burnaby B.C.

Try polishing the comutator (where the brushes run) in the alternator.
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!tom · Posted: Thu Apr 16, 2009 5:20 am Post subject:

Brockoli · Posted: Thu Apr 16, 2009 7:43 am Post subject:

i thought alternator whine comes from electromagnetic interferece. This electromagnetic field is caused when power flows thru a wire. If this field is too close to a speaker wire/RCA cord the electromagnetic field interfers and causes the whinning noise in the stereo that is dependant on RPM.

I have had this happen to me with previous ICE(in car entertainment) setups.

Things to check/change:
-are there power wires close to speaker wires/RCA wires, if there are and this is unavoidable intersect the power wire and the speaker wire perpendicluar to one another, to make a X pattern. This will help eliminate the whine, you can use posicle sticks to make sure it stays in the X posistion. I leant this from a professional car audio installer.

-Are your RCA wires shielded? Are they car audio RCA wires, this make a huge difference. I once cheeped out (haha, once

, okay maybe a couple times) and bought home audio RCA wires that were not shielded and had big gold connectors on them. The whine was terrible. I band-aided the problem by running a ground to the big gold plated connectors. I did this by taping a wire to one of the gold connectors and grounding the wire, I know, SHADY!. It fixed it a bit but not entirely. I eventually bought proper triple shielded car audio RCA's and it fixed it. I gave the sweet home audio RCA's to my Dad for his home theatre system.

-Is your power wire for amp(s) run on the opposite side of the car from the RCA's. If you have an amp? This will help reduce electromag. interference.

-Is your deck properly grounded. And i mean properly, not the shady 30 gauge wire that is stock in ford taurus', ask me how i know? I always run a new ground to direct metal with a reasonable thick wire.

-Are you running an auxially input for an ipod/mp3 player. I am in my 924 and my girlfriends '09 WRX and if the iPod is not connected there is terrible whine/feedback in the speakers. I just connect my iPod even if I am listening to a CD/radio. This fixed the problem.

I dont have a problem in my 924, but i do not have any amps(yet). I ran all new speaker wire,power+ground wire in my car aswell, and tried to keep the speaker wires away from power wires the best i could. Also, the longer the distance a speaker/RCA wire runs directly beside a power wire the worse the interference.

Hopfully this helped. Keep us updated!
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flosho · Posted: Thu Apr 16, 2009 9:49 am Post subject:

I didnt read brockoli's post... however.. ok, so I just read his post, he's dead on(at least from my experience as well).

I've experienced the noise because the rca or speaker wires are too close to the 12v+ line.

Not sure of the setup you have in your car Vaughn, but if it includes an Amplifier then id bet your life on the power/rca interference.

run the power line on one side of the car and the rca/speaker wire on the other.

No need for a capacitor unless your lights dim.
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Ozzie · Posted: Thu Apr 16, 2009 12:17 pm Post subject:

Instal filters to your amp.
Sorted my problems out.
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924RACR · Posted: Thu Apr 16, 2009 9:59 pm Post subject:

Yes, I'm actually running 2 amps - one 4-channel for the speakers, and one bridged for the sub.

Good call on the RCA/power interference, guess I have to check that next. One problem, however, is that in diagnosing, I noticed that if I unplug the RCA patch cords from the head unit, the noise is gone. I would expect that this would indicate that they're not bringing the noise, unless the amp turns off with them unplugged?

For comparison, plugged in with the head unit muted, I have the noise.

Yes, it does rise and fall with engine speed.

No, the patch cords are not real great... ironically I do have one very nice patch cord, Monster Cable purchased for the sub amp! They are all (power and patch cords for both amps) currently routed along the passenger door sill area; I will try re-routing them, then, see where that gets me, and also try swapping in the big Monster Cable sub patch cord over to the main speaker amp.

Thanks guys, will post back with results (probably Sunday)...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

924RACR · Posted: Sat Apr 18, 2009 2:55 am Post subject:

No joy. Tried moving the patch cables to the center tunnel area; no change.

Tried swapping in the one good Monster Cable line (previously on the rear/sub amp) - same problem, no improvement.

Still have whine.

Tried using a different ignition signal, the one from the radio relay (imagine!) - no improvement.

Any more ideas??
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Min · Posted: Sat Apr 18, 2009 3:20 am Post subject:

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

Give us some more info to help diagnose.

Is noise just on radio only, CD or MP3, or both?

Does it occur with head unit only, just with amp on, or either?

At idle does it sound more like static, raising in pitch with RPM or a higher frequency whine at idle that also increases.

Does it remain about the same volume level at all RPMs or get louder?

Is it louder if you turn high beam, or demister on?

What if you turn on HVAC blower?

EMI could be transmitted via RF or AC signal on DC line. Also all larger amps (over about 50W PMPO or 25W RMS) use a DC-DC converter that oscillates at HF although it shouldn`t vary with RPM it may with increased output power from alt.

Have you tried with the B+ lead disconnected from alt?

924RACR · Posted: Sat Apr 18, 2009 4:48 am Post subject:

Min - you mean grounding a shield on the RCA/patch cables, I think?

Noise is on all settings; radio, MP3/Aux, and CD, as well as when muted!

All speakers are run from amps, so without both head and amps on, no noises, no nothing - can't evaluate.

Pitch is constant at idle, when idle is constant; it's directly tied to rpms. Volume is constant regardless of rpms; only changes based on amp gain settings.

No change with high beams or demister unless those affect idle speed.

HVAC blower makes no impact whatsoever (doesn't change idle).

With engine off, but head unit/amps on, there is no whine.

I have not tried with the alt disconnected yet, good point, will try. I assume you mean the main cable, not the small one, by B+?
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype