I'm getting static in my AM radio that I do not understand.

WITH THE ENGINE OFF
I can set the key to ACC and the radio works perfectly -- well, it works as
well as an AM radio can be expected to work. But, when I set the key to ON
(but not START), the radio instantly produces a loud hiss, or static.

The Power source is the same, but the truck's own electronics create some
kind of noise. After the motor starts, the sound remains the same and is not
associated with the spark plugs - remember, the noise is present even when
the motor is not running.

"lugnut" <lugnut (AT) bellsouth (DOT) net> wrote

A couple of add-ons:
The electric fuel pump is often a source of interference for AM. On
some models there is a TSB fix for this.
I have very successfully corrected interference problems on Ford radios
by replacing both the antenna and coax, using a better shielded coax.
The factor Ford AM radio in many of the 90's cars and trucks I've fooled
with is itself not helpful. The broader the tuning, the more fidelity you
have, but the more open the input stage is to interference. It seems that
most aftermarket radios do a better job of filtering interference than the
factory radios I've fooled with.

CJB

"Jeff Strickland" <crwlr (AT) yahoo (DOT) com> wrote

electric fuel pump running?

Eisboch

Eisboch wrote:
Doesn't the pump only run 'on demand' to keep the fuel system
pressurized? It would only run for a second or two if the engine was
not running.

One thing that could be running is the fan. Is the static frequency
related to the speed of the heater/ac fan? As CJB suggested, various
ferrite filters could fix the problem but you should make sure you have
proper grounding. There should be a ground lug on the back of the
stereo and that needs a good strap to chassis. you might test this by
taking a piece of wire and making a temporary ground strap between the
unit and chassis to see if it makes a difference.

I am assuming that the radio used to work properly and you have also
checked the antenna connections.

Stephen N.

"CJB" <colonyparkwagon (AT) excite (DOT) com> wrote


I should have mentioned that my radio is an aftermarket unit ...

On Thu, 06 Jul 2006 12:27:17 -0400, lugnut <lugnut (AT) bellsouth (DOT) net>
wrote:


Not a canister filter, you need a in line iron core choke to remove
the "line noise" from vechicles electronis. If you are so inclinded
you can unstall some .01ufd bt pass capacacity in power wires feed ECM
and other electronics as this can help sometimes too. (you want the at
the actual power feed into unit)
-----------------
The SnoMan
www.thesnoman.com

On Thu, 6 Jul 2006 12:45:24 -0700, "Jeff Strickland" <crwlr (AT) yahoo (DOT) com>
wrote:


There lays part of your problem. Some after market radios do not
filter the input power very good if at all. Install a inline filter
chake as mentioned above in postive power leg feed.
-----------------
The SnoMan
www.thesnoman.com

Yes, I suggest it could be the electric fuel pump causing the interference.
Do this, pull the antenna lead of that radio and that will tell you if the
noise source is coming down the antenna leadin or from the power line. I
will bet on the power line which can be filtered with a good choke
capacitor type of filter. Try radio shach for that. If you find that it is
coming dwon the antenna then the problem might be a bit tougher and you
mnay need to find the source and bypass at the source such as the brushes
is a motor or what ever is causing the radiation of radio frequency
energy. Remember, without me getting too techinical, FM modulation varies
the frequency at a audio rate whilst AM modulation is varied at an
amplitude rate. With FM the nise id "clipped by a limiter". In am not so
and since most noise if AM, it is best killed at the source. Hope this
helps.

Bill

The HVAC blend door control circuit was causing interference on our
1997 Ford Expedition. As you changed the temperature knob
you could hear the radio static change. Fortunately it was under warranty.

-CT

"wackerman" <wackyman@> wrote