Radio Disturbance

TheGeneral

New Member
Joined
Mar 22, 2005
Location
Wilmington
Ive got an XM radio that plugs into the cig lighter for power. As long as the motor is turned off the signal comes in clear, but as soon as I start the truck it starts squeeling this super hi pitch whine. I know they say spark plug wires can cause radio disturbance but my trucks a diesel... I thought maybe it was the lighter going out but I have a cig lighter and an accesory outlet and they both do it. Anybody know of any kind of electrical problem that could casue this??

Thanks
Justin
 
How loud is the whine.
Is it overbearing or almost background?

If it is the background squeal it is an xm problem.
Well documented online.
With vehicle cranked and alt output you are getting full power (~14.5) at lighter. With vehicle off you are probably getting more like ~12.

I solved mine by cutting and splicing in a small burglar alarm resistor into the power wire between cig lighter and XM.

I was told it wouldnt work and would void warranty etc, but going strong 9 months later

YRMV
 
The wine overpowers the music it's so loud and it gets worse at high rpm, so I guess its the voltage problem. What kind of resistor do I need and how do I figure out which of the two wires I splice it into? Other than wiring lights and stuff Im pretty sucky at all things electrical.
 
Does it change pitch with RPM? Could be noise in the power from an electric fuel pump, the alternator, etc. Ground loops between the antenna ground and receiver ground can induce them, too.

The first thing I'd try is running wires straight from the battery to your XM receiver and see if it still makes noise when the truck is running.
 
If it changes with RPm and gets louder at speed, it is getting induced voltage disturbance from something else.

The Xm problem is barely audible.
many users wont even complain of a whine just headaches when they listen for extended periods of time.
 
Okay so I went out the the truck and did a little more concrete observation of the problem. When the truck is off its fine. Sitting at Idle it sometimes is okay and sometimes is not. Once I start going it starts to whine and dosent stop untill I turn the truck back off, It doesnt change pitch or intensity with high rpms, it just starts once the rpms get above about 1200. Once the music gets into the lyrics it dosent overpower the music as much as it does during soft instramentals, It does give you a headache after a while of listening to it.

I went and plugged it into another truck (same make and model) and it still did the same thing, so I think I'm going to try and wire in the resistor and see if that fixes it before I go tearing my wiring apart. What kind of resistor was it that you used? Did you solder it inline or just butt splice it?
 
I just crimp spliced it in.

Honestly I dont know the rating, I just grabbed a resistor out of my bag ( I was doing alarm work full time at thee time) they are all fairly small.

I could untape it and read it this evening if you need and find out exactly what I used.
 
Try running power direct from the battery with both power and ground wires. Keep them away from as many other wires as possible.
 
Ill try running a couple wires from the battery to the cig lighter tonight. I figured plugging it into another truck would be about the same thing but anything is worth a try.
 
Sounds like ground loop noise, ie. difference in potential between devices. Check your grounds. Also could be defective diode in alternator.
 
Interesting that your XM is having that trouble. I've never had XM before, but I've had several different Sirius receivers and never heard a peep of a whine out of any of them. Of course that really doesn't anwser your question...
As stated previously, your problem is almost certainly caused by alternator whine. The best way to fix it is to get rid of the whine at the source, but that can be a frustrating and possibly expensive troubleshooting process and it sounds like that's not what you're loking for. On the other hand, the easiest way to get rid of it will be to install an inline noise suppressor, like this one from Crutchfield:

http://www.crutchfield.com/cgi-bin/prodview.asp?I=003S15A

It will involve cutting off your cigarette lighter plug and wiring it to the fuse box, via this noise suppressor, but that's really better anyway. It's not that hard to do, and it will definitely get rid of any noise coming in on the power cable.
 
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