Alternator Suppressor

[trailblazzer]

Hi everyone,

I've got an alternator whine coming from my old Nissan Pulsar at high speed, rising and falling with acceleration. Does anyone know how to fit a suppressor to the alternator? I've read very mixed reports. Some saying connect to a mounting bolt and the positive terminal, and then others saying absolutely do not connect it to the positive terminal... I've got one of these ready to go...

[colin_p]

I've not had to deal with this for many years but when I did, the usual and best fix was ensuring that the stereo (assuming that is the question) is properly grounded to earth / the chassis. I've run dedicated stand alone earth leads before.

Also, are you sure it is the alternator and not something on the ignition system?

[trailblazzer]

LOL Dont talk to me about grounds I've spent about 6 months chasing my tail there, cleaning terminals, adding new ones. Its a really odd noise actually. It still comes through when the stereo is off. On other cars I've worked on turning off the stereo usually stopped it. Others I solved with grounds or filter toroids on the ignition wire into the stereo. But this one has me beat! Only happens when on the accelerator, if the car is freewheeling at the same revs, silence.

[colin_p]

trailblazzer said:

LOL Dont talk to me about grounds I've spent about 6 months chasing my tail there, cleaning terminals, adding new ones. Its a really odd noise actually. It still comes through when the stereo is off. On other cars I've worked on turning off the stereo usually stopped it. Others I solved with grounds or filter toroids on the ignition wire into the stereo. But this one has me beat! Only happens when on the accelerator, if the car is freewheeling at the same revs, silence.

Ok then, i'll take a further punt on the * ignition system;

Spark plugs - are they the correct type. i.e. resistors vs no resistors, usually has an 'R' somewhere in the plug number?
Ingition leads - again, are they correct i.e. supressed?
Coil - same, is it the correct type.

• assumes it has a traditional ignition system, with leads and not coil packs.

[trailblazzer]

Hadn't thought of the leads or plugs. Thanks! I will check em out. How would I tell if the coil and leads are the problem? I've actually got resistance tolerances for what the leads should be, just measure that or is there more to it?

[colin_p]

Don't know but any Carlos Fandango looking aftermarket stuff would probably be highly suspect.

[GreenV8S]

trailblazzer said:

I've got an alternator whine coming from my old Nissan Pulsar at high speed, rising and falling with acceleration

trailblazzer said:

It still comes through when the stereo is off

Are you chasing electrical noise or mechanical noise?

If it's electrical, where are you hearing it from?

[colin_p]

Hmmm.... more thoughts....

How about about the fuel injectors? The clue there is you hear the noise when on throttle.
Fuel pump.

But, I don't know anything about that particular car, for all I know it might be carb'd with a mechanical pump.

[trailblazzer]

It could well be mechanical noise. I've theory I've chased was a vacuum leak somewhere. But after lots of testing and stuff I found nothing.

It is injected. It's a late model Nissan Almera basically. With a ga15de engine for any aficionados out there...

It sounds exactly like electrical noise I've cured before. I have one of these cheapo suppressors now so does anyone know how to fit it? It's just a capacitor is a pretty standard way to cure electrical interference.

I'm not sure where is coming from its only really noticeable at about 60km/h and between 101- 105km/h. So it's hard pin point it. Also the car is built like a bean tin so it's quite noisy at speed anyway.

Edited by trailblazzer on Saturday 15th September 21:21

[GreenV8S]

You seem to be working on the theory that you're chasing an electrical noise, but if it isn't coming from the speakers I don't see how it could be.

[trailblazzer]

It could be in the speakers. I can't tell.

[GreenV8S]

Wouldn't the speakers be unpowered with the stereo off? If you have access to disconnect the speakers you could tell for sure. Alternatively, if the noise is loud enough to hear then it ought to be really obvious if you record close by the speakers while it's happening.

[trailblazzer]

Exactly. The car has an aftermarket alarm fitted in wondering if it's possible the siren speaker of that might be the source.

Anyway. If it is alternator noise. A suppressor at the alternator should make a difference. I have a suppressor ready to go, do any of you know where to connect it?

[sparkythecat]

Undiagnosed tinnitus?

[GreenV8S]

trailblazzer said:

Exactly. The car has an aftermarket alarm fitted in wondering if it's possible the siren speaker of that might be the source.

Anyway. If it is alternator noise. A suppressor at the alternator should make a difference. I have a suppressor ready to go, do any of you know where to connect it?

I think you're wasting your time doing that unless/until you have confirmed it is an electrical noise. Even when you have, trying to filter it out electronically will need you to work out which component is being affected by the noise and add one or more filters and noise suppressors to its power supply close to it to eliminate the noise. You wouldn't get anywhere adding small caps to the alternator itself since you would be trying to filter a 100 Amp circuit, and obviously those little caps aren't going to do that.

[Penelope Stopit]

Have you tried disconnecting the alternator and then running the engine?

You very likely know that Alternator interference sounds like a whine and ignition interference sounds like a crackle