Radio static from rear defroster

[Soleman20]

Anyone ever get static on the radio when the rear defroster is on? I do and it is really annoying. I know on P10's that the rear window has a secondary antenna imbedded in it for improved reception. I think the antenna and the actual mast on the car receive the AM/FM signal simultaneously. Any clues??

[A380Driver]

Originally posted by Soleman20
Anyone ever get static on the radio when the rear defroster is on? I do and it is really annoying. I know on P10's that the rear window has a secondary antenna imbedded in it for improved reception. I think the antenna and the actual mast on the car receive the AM/FM signal simultaneously. Any clues??

Umm the second antenna is imbedded in the winshield

If you recieve static on your radio the best bet would be to check to see if the antenna is grounded properly to the car. A loose ground would definatly cause static.

[Stogie82]

I have the same problem. I only get static when the rear defroster is on I cant figure out why but then again I havent really tried now i just don't use it but it would be nice to know why it does it and how to fix it.

[A380Driver]

Originally posted by Stogie82
I have the same problem. I only get static when the rear defroster is on I cant figure out why but then again I havent really tried now i just don't use it but it would be nice to know why it does it and how to fix it.

Well, its just like any other high powered current that runs through a wire, it creates that EMF (electro magnetic field)..so it creates a distrubance, especially with AM stations. Think of wrapping an electric blanket around your antenna (kinda)

Not really much you could do execpt make sure your antenna is really grounded well.

[Stogie82]

ok that make sense but it does it real bad on some FM stations it might be that I am 60+ miles from the source of one particular station and I am lucky to get it anyway. Also where is the antenna grounded is it just in the trunk or does it ground by the radio itself too? Thanks for the info

[eeyore]

This is caused by a dodgy contact on your rear heater. Check the connection to the rear demister. It'll probably be either loose or corroded. tighten it or brush it up appropriately...

What'll be happenning is as follows:

1. you turn your demister on, which draws quite a large current through it.
2. because of the dodgy contact, the current will be jumping across an air gap and/or dirt.
3. This sparking effect broadcasts high-frequency "white" noise both through the air (into the antenna) and back down the 12v line (into your radio).

Here's another little test: start the engine, turning your main-beams on, plus fog lights, spot lights and any other current-drawing device you can find (apart from the rear demister). Does the noise appear? If so, then it's the supressor on your alternator (and/or radio 12v line) that's failed. The noise gets louder with more current being drawn from it (and the rear demister will draw it's fair share).

Hope this helps.

Mat

(P11 owner and electronic engineer)

[DJ Hotpokit]

I get the same problem too as soon as I turn on the rear defroster, all I hear is static I can barely hear the radio over it.