Just wondering if anyone might have some advise for me...

02 4runner. Whenever the radio is on and I turn the headlights to 'on,' I get a constant hum through the speakers.

I have the factory DRL's obviously, but it only happens when the headlights or even just 1 click over to the running lights. If I turn them off, it'll go away.

I recently changed the belts, and cant remember if it happened before that and I didnt notice, wasnt sure if changing the belts could cause something like that.

Any help would be appreciated. My only guess would be to check the grounds, sure that'll be fun getting to behind the radio.

 

there are some wires from the stereo making contact with a wire from the lights...

 

Changing the belts should have no effect on the radio noise. I would say check the ground 1st. Are you running an amp or is it the stock radio? Usually a hum is caused by a bad ground I believe.

 

Just factory everything on it. I figured some kind of ground may have been busted loose. I'll check everything maybe tomorrow if I get a chance, and hopefully it'll go away!

 

i say a ground

 

I checked the main ground... the battery, and a few engine ones, and they all seem tight. So I guess I may have to pull the radio out and see if maybe something behind there is lose

 

If your connectors to the back of the radio headunit are loose could cause noise.Also when you turn the lights on it also powers the backlighting on the radio display,so no noise untill you turn the lights "on".

 

Sorry for resurrecting an old thread but I am having the same problem. Can anyone help me know what to look at to fix it? My grounds look good. Could it be my oem radio kicking the can?

 

It could be a alternator rectifier pack going out and allowing A/C to leak out under load.

Another way to try this is instead of the headlights, turn on the rear window defroster to put a load on the alternator. If you don't hear the hum then its going to be something else.


FOG

 

When you turn the headlights on, the radio lights up. Go from there. Illumination wire? Disconnect that and see if the noise goes away.

 

Thanks for the input guys. Scottish if it would turn out to be the wire how do I go about replacing it?

 

Also I was looking to replace the factory radio with an aftermarket. Would this fix the problem?

 

It might fix the problem. Could be the ancient head unit, the wiring, or the separate amp behind the stereo.

The new head unit install is super easy, so it is worth a try. I did my 2001 in like 15 minutes...

 

What others have said is headin in right direction - you should try to isolate the problem. I can't remember if the stock amp has its own power or if it depends on power from the HU, but if it does have its own power, remove the signal source from the headunit to the amp to see if the noise is still there

 

Thanks for trying to help guys. I'm going to try and figure it out this weekend. Also could it be that some wires are touching that shouldn't be? The last time I had the dash apart was to unplug the motor for the power antenna because it was broken and I got sick of the motor running. Could I have possibly done something when I unplugged that?

 

I don't have many ideas that haven't been mentioned already but if everything is well grounded and you've got good connections you might just be picking up some interference. If that's the case you can buy a little "filter" that connect inline and it will take care of it. They cost about $5 at RadioShack or any other audio shop.