AM Radio Static
AM Radio Static
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
I must assume you still have the stock headunit since you didn't mention an aftermarket one. Stock radios usually have better AM antennas then aftermarket any way.
I would start by adding another ground from the motor to the firewall. I would use 4ga wire just to get a good start on the big three upgrade. Once that is done and if you have more static, I would check the voltage going into the radio using the chassis of the radio for the ground and compare it to the voltage on the battery. They should be very close, if not, you still have a ground issue to resolve. This would be a good time to run a 4ga wire from the battery to the body. My truck had an unused bolt right next to the battery that I used.
I would start by adding another ground from the motor to the firewall. I would use 4ga wire just to get a good start on the big three upgrade. Once that is done and if you have more static, I would check the voltage going into the radio using the chassis of the radio for the ground and compare it to the voltage on the battery. They should be very close, if not, you still have a ground issue to resolve. This would be a good time to run a 4ga wire from the battery to the body. My truck had an unused bolt right next to the battery that I used.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Sounds more like you have a bad diode in the bridge rectifier in the alternator.
The more load, the more the alternator has to put out, and a bad diode will show up as a bad waveform from the alternator. That causes static on AM radios.
Does it also do it if you plug in the cigarette lighter and hit the brakes at the same time? Or anything else that would put a good load on the alternator like turning on the AC?
The more load, the more the alternator has to put out, and a bad diode will show up as a bad waveform from the alternator. That causes static on AM radios.
Does it also do it if you plug in the cigarette lighter and hit the brakes at the same time? Or anything else that would put a good load on the alternator like turning on the AC?
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
That is a good point - any weak AM signal usually has static in it that matches the alternator speed. Increase the load, more static.
It might be "normal" if the signal is weak to begin with.
It might be "normal" if the signal is weak to begin with.
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5th Wheeling
Joined: Aug 2003
Posts: 26
Likes: 0
From: Massachusetts
I have the same problem. If the radio station doesn't have a real strong signal, I get bad static by just turning on the parking lights. Just put in a new stereo with BT and the AM is just as bad. Also when on a call the person on the other end will hear noise when the turn signal or lights are on.
Noticed that the ground is tied into the wiring harness. I may try running an extra ground wire to the chassis somewhere.
Noticed that the ground is tied into the wiring harness. I may try running an extra ground wire to the chassis somewhere.
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Freshman User
Joined: Feb 2008
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From: DeWitt, MI
I am having the same problem with my 01 F350, but with FM stations. It seems to change pitch with RPM. Does that mean a bad ground? I know it is really annoying. I haven't tried to fix it yet, because it is cold and snowy, and I would have to do it in the driveway. It is times like this I wish I didn't have a crew cab long box-not really, just wish we had built the garage bigger.
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
It's likely some kind of ground differential between the metal under the antenna and the radio. One thing to check is turn the radio volume all the way down and listen for the noise. If it's still present without the music, then it's after the amplifier in the radio. If it goes away with the volume, then it's pre-amp in the radio and likely something with the antenna or amplifier.
You can never have too good of a ground in any case.
You can never have too good of a ground in any case.
Cargo Master
Joined: Jan 2007
Posts: 2,243
Likes: 79
From: Roman Forest, TX
Uh...what is this "AM" thing?? 
I think I have listened to AM once since I got my truck. I really wanted to listen to that Cowboys game. I actually got to hear almost all of it from San Antonio to Houston (the station was out of San Antonio). I only lost the signal about 15 miles from my house.
Okay, sorry for the drift. I think all the others have pretty well covered it up there. Personally, I've never had much luck getting rid of it when it was bad. I have a good aftermarket now (Pioneer) and get no static (other than standard AM stuff).
I think I have listened to AM once since I got my truck. I really wanted to listen to that Cowboys game. I actually got to hear almost all of it from San Antonio to Houston (the station was out of San Antonio). I only lost the signal about 15 miles from my house.
Okay, sorry for the drift. I think all the others have pretty well covered it up there. Personally, I've never had much luck getting rid of it when it was bad. I have a good aftermarket now (Pioneer) and get no static (other than standard AM stuff).
Junior User
Joined: Nov 2008
Posts: 94
Likes: 0
radio static
I also have static in my radio when headlights are on. i've tried turning off the lights and the static goes away,i've turned the heater on high (with lights off)to add load to the alternator,no static..this static is on strong stations as well as weaker ones. has anyone found a sure fix for this?..thanks,Dave
Last edited by david0505; Mar 15, 2012 at 10:41 AM. Reason: spelling
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