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Old 02-19-2002, 12:42 PM
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Default Radio static when running

With the Jeep running, I'm getting an annoying static sound. I replaced the antenna, and grounded the stereo (Kenwood) right to the battery. I have the TR upgrade, and the stereo is a direct replacement for the last one (water damage). The last one had great reception, no noise. This is driving me nuts, what causes this? I have brand new 8mm wires, AC Delco resistor plugs etc. It is not the type of interference that goes up and down with the rpms, more like a a steady static pulse. PLEASE, NO "WHO NEEDS A STEREO JOKES!" I've read them all before.

'84 CJ-7, 4.2, 3.5" Lift, 31's, YJ tub, TR upgrade, Moser 1 piece, LED's.
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Old 02-19-2002, 03:45 PM
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Default Re: Radio static when running

Take note of where the Capacitor (Referred to as a 'Condenser' by some) is in the drawing.
Adding one of these will help your problem, and should be under $5 at any parts store.
Make sure the case of the capacitor is grounded.



If you are getting a 'Snapping' sound, take your distributor cap off, and use a dab (light coating) of dielectric grease on the rotor nose, the cap center electrode (button), and the terminals inside the cap.
Sometimes corrosion or cheap cap terminals will cause the noise.
Dielectric grease is also called 'Tune Up Grease' at the discount auto stores. About $2.

Make sure all of your spark plug wires are well connected to both the cap, and the plugs.
Good wires will make a 'Snap' when the make proper connection.

Check to make sure the coil wire is connected properly. This is the source of the 'Buzz' some people hear.

Check your engine ground.
If you ground strap to the engine isn't getting good connection, or if the ground is too small, you will get radio noise.

Make sure your antenna cable isn't near a spark plug wire....

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Old 02-19-2002, 04:31 PM
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Default Re: Radio static when running

Thanks TR, I'll take a look at it this weekend. What bothers me is that nothing changed on the Jeep except the stereo, which was a direct replacement. But it does work fine when the engine is off, so it must be the Jeep.

'84 CJ-7, 4.2, 3.5" Lift, 31's, YJ tub, TR upgrade, Moser 1 piece, LED's.
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Old 02-19-2002, 06:26 PM
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Default Re: Radio static when running

No such things as "Direct Replacement" radios.
Every radio type will have different receive characteristics.
This one just happens to be a little more sensitive, and is picking up something in a frequency range the factory one was immune or not sensitive enough to 'hear'...

One thing I forgot, many of the early factory radios had current supply noise filters, this one being intended for use in a later model vehicle may not have such good Capacitors/ noise filters built in. You may have to add a capacitor to the power supply for the radio to take the alternator noise out, if that is what it turns out to be...

It's easy to find out, just unplug the alternator and start up the engine and listen...
If the noise goes away, it's the alternator.
If the noise stays, it's probably the ignition.

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Old 02-19-2002, 11:51 PM
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Default Re: Radio static when running

from my understanding you can have two sources of static(which is what tr's suggestions hit)they are thru your ign.wire or actual r.f. energy created by one of your components. to eliminate the ign.wire source is thru filters using caps and or coils to "short" a.c./r.f. to ground. like the one on your ign. coil and also aftermarkets that are installed on the pwr wire going to your equipment. on the airwave r.f. its harder you look for like what tr said about coil and sparkplugs.also altenators but ussally that will vary with speed of motor sometimes. though it could be another peice of elec. equipment that you have on doing this like a c.b. or some type of amp thingy for example. i could be wrong but i thought thats how it was explained to me one time.

taco
78cj7
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Old 02-20-2002, 12:10 AM
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Default Re: Radio static when running

Hey TR...

On the same subject, I get a LOT of RF out of my MSD (6 digital, MSD Distrib, MSD 8mm wires, and E-core coil) setup. Basically it follows RPM's when the engine is running. My grounds are GOOD, at all points. Will try the dialectric grease tomorrow.

In that drawing, where would I put the cap as it relates to my system? Or does it even apply? If so what values for the cap?

I am already running a pretty healthy cap accross power/ground for the MSD unit itself.

'83 CJ-7 nothing original but the tub and axle tubes
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Old 02-20-2002, 12:51 AM
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Default Re: Radio static when running

Try the dielectric grease on the rotor nose, center button, and terminals.
The Capacitor (that big friggin' MSD cap!) in the power to the MSD is the thing to have.

You have a "Leak" or air gap somewhere.
Find it and kill it.

The cap at the coil positive will do you no good with the MSD set up.

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Old 02-20-2002, 03:11 AM
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Default Re: Radio static when running

You got just the one, the big red MSD cap with the screw-in lugs, something like .25-.50 farad or equally ridiculous.

Was also thinking about putting some larger filtering caps in parallel with my power distribution/fuse blocks to clean it up a bit there too.

'83 CJ-7 nothing original but the tub and axle tubes
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