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Building a simple Alternator whine / ignition filter

imustbenuts

Member
Dec 11, 2010
6
0
11
It didn't help me

I am getting frustrated with this! I installed a cobra 75 wx st. Engine noise is very annoying! Does anyone have any other suggestions I can try??? Any help would be appreciated!
 

Robb

Yup
Dec 18, 2008
11,433
3,583
323
Silicon Valley CA, Storm Lake IA
I am getting frustrated with this! I installed a cobra 75 wx st. Engine noise is very annoying! Does anyone have any other suggestions I can try??? Any help would be appreciated!

Then check every ground and consider replacing your alternator. If it is as bad as you claim; it might be ready to go anyway. But you must be sure first. Lots of things make noise. You will have to go thru the main three offenders. One more thing - you can put capacitors on the charging system, ignition system, and fuel system. Either your vehicle didn't come from the factory so equipped - or they need larger capacitor values - or are faulty.

The best way is to check each system independently by removing the right fuses from the fuse box with the key on. This works for the fuel system. If the fuel pump isn't making RF noise when power is removed; then it needs to be suppressed by a capacitor.

Next, remove the field wire from the alternator and check for RF noise. If noise is still present; then it might well be the ignition system that needs more suppression. If you don't know your way around a car - then forget about doing it yourself and take it to a shop and see if they can't sort it out for you.
 

GunSlinger338

Active Member
Feb 26, 2006
101
1
28
Around Tha Dome
i finally got around to building/installing this in my 06 ford diesel !!
It worked like a charm !!!

I can actually talk on the radio again with out tha all to familiar "where's the lawn mower" response I have grown accustomed to hearing !

thanks for the info
 

MrSuburban

Guest
May 25, 2010
393
9
28
i finally got around to building/installing this in my 06 ford diesel !!
It worked like a charm !!!

I can actually talk on the radio again with out tha all to familiar "where's the lawn mower" response I have grown accustomed to hearing !

thanks for the info

Were you getting alternator noise or fuel pump? Most common these days is fuel pump, be interesting if it helps with fuel pump noise.
 

mackmobile43

Jock Supporter
Feb 11, 2008
6,697
402
0
I am getting frustrated with this! I installed a cobra 75 wx st. Engine noise is very annoying! Does anyone have any other suggestions I can try??? Any help would be appreciated!

Disconnect your antenna and see if the noise goes away and if it does no amount of power line filtering is gonna help.

You will have to find the noise source and kill it there.
 

MrSuburban

Guest
May 25, 2010
393
9
28
Disconnect your antenna and see if the noise goes away and if it does no amount of power line filtering is gonna help.

You will have to find the noise source and kill it there.

agreed if it is the fuel pump you gonna have to put some caps as close to the pump as possible where the wire enter the pump under the vehicle.

turn the radio on and turn the key on dont start the car do you hear the noise then? Maybe someone already said to try this i was to lazy to read all the posts
 

xPosTech

Gimpy Gadgeteer
Mar 20, 2011
17
0
11
SE Texas
First thanks Moleculo, Beetle and Jim KB1MVX for the filter instructions. Much appreciated.

Would there be any benefit or detriment to putting this in a shielded box rather than plastic? I only ask because room is a little tight in the truck under/behind my Galaxy. I have both the plastic box called for and an aluminum one that's slightly smaller.

If it won't degrade the filter I will use the aluminum box. I was just wondering if shielding the thing would improve it in any way. I have a hunch it won't help it a bit considering all the open chokes I see in amps.

Ted
 

nicksort

Member
Jan 23, 2011
13
0
11
I just saw this thread and I am going to try it for the ignition and fuel pump noise in my diesel truck but I have a quick question.

Red into the box is power in?
Red out of box from the cap to the radio?
Black from cap to the ground?
Is this correct?
 

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,059
1,388
283
I just saw this thread and I am going to try it for the ignition and fuel pump noise in my diesel truck but I have a quick question.

Red into the box is power in?
Red out of box from the cap to the radio?
Black from cap to the ground?
Is this correct?

Yes. It may work on the ignition noise, but I doubt it will work on the fuel pump noise. It's worth a try, though.
 

nicksort

Member
Jan 23, 2011
13
0
11
thanks to both of you for the quick reply back .....

Also can the black be co-connected to the same ground junction where the radio is connected or will that cause a conflict?
 

nicksort

Member
Jan 23, 2011
13
0
11
Well i purchased the parts in the list but I needed to make a change in the box size, I needed a larger size. I could not get the finished project into a 6" long box, I needed to go to a 7" box. I was worried I would break the cap leads twisting it into the 6" box. I will install it this week and let you know how it works. I also did the test on removing the antenna and see what type of noise I have, yes I do have some noise, I think it may be from the power feed I have to the radio which is through the lighter. Because of this I also purchased parts to bring in the power and ground directly from one of the two batteries under the hood to another project box and I will install a power rail or strip junction (12x) inside of it and then connect the radios to that. I also have added extra ground connections from the antenna mount to the battery ground directly. I will let you know how it all turns out.

IMG_20110801_095141inthebox.jpg
[/IMG]
 

nicksort

Member
Jan 23, 2011
13
0
11
Well I did what I said I would do, I cleaned up the wiring and and ran it direct to a box under the seat and connected everything there. The good news is doing this dropped the noise level down quite a bit.
Unfortunatly adding my new alternator noise filter did not do anything for the small amount of noise I am getting with the new setup. Next I will install it into my old 20yr old klunker I drive when I want to give my truck a break.....
 

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