ground loop problem

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daught

Member - Posts: 5

Joined: November 02, 2007

Location: Ontario, Canada

Posted: November 02, 2007 at 3:33 PM / IP Logged

I just installed an XM radio in my car. The unit is a Delphi roady XT. If I connect it to my head unit through the AUX in I get a lot of ground loop type of noise. If I send my signal through the FM transmitter there is no problem. Also If I use my laptop to send signal to the head unit AUX in there is no problem either. Basically I don't get any noise except if I have the XM receiver going to my HU through the AUX in. I am quite willing to bet that the XM receiver power adapter (12V to 5V) is the culprit here. Any idea on how to fix this without using a ground loop insulator?

sarcomax

Copper - Posts: 276

Joined: November 09, 2005

Location: California, United States

Posted: November 02, 2007 at 4:11 PM / IP Logged

You can try hard wiring the adaptor to wiring in the car by either soldering wires to the connections, or spending three bucks and getting a female cig lighter port and wiring that in. I have had mixed success with this in the past. Make sure that you have a good ground.

daught

Member - Posts: 5

Joined: November 02, 2007

Location: Ontario, Canada

Posted: November 02, 2007 at 7:54 PM / IP Logged

Would wiring the adapter to the HU lines give he best results?

csnut18

Copper - Posts: 196

Joined: January 27, 2007

Location: United States

Posted: November 02, 2007 at 8:07 PM / IP Logged

Yes you shouldt take power and ground for the xm from the same spot as the hu.

daught

Member - Posts: 5

Joined: November 02, 2007

Location: Ontario, Canada

Posted: November 02, 2007 at 10:47 PM / IP Logged

I have another idea/question. Lets say for educational purposes my amp and HU made such noise. For simplicity rather than running some heavy gauge wire back and forth to ground them at the same point, could you just run a very small gauge wire between HU and amp ground to get rid of the ground loop?

Also for my situation could I just splice s small wire between the cig lighter adapter and the HU ground?

csnut18

Copper - Posts: 196

Joined: January 27, 2007

Location: United States

Posted: November 02, 2007 at 10:51 PM / IP Logged

Cut the cig lighter end off leaving you with just the bare wires. One wire is positive and one is ground. Install a 3 amp inline fuse on the power wire. Now just splice that wire into the power wire going to your radio and do the same for the ground wire making sure they are both being taken from the radio power and ground.

daught

Member - Posts: 5

Joined: November 02, 2007

Location: Ontario, Canada

Posted: November 02, 2007 at 10:55 PM / IP Logged

Thanks for the reply. That is what I will do.

Just to feed my curiosity would what I have said above work or not? I am not really interested in going this route, it is just so I learn something.

csnut18

Copper - Posts: 196

Joined: January 27, 2007

Location: United States

Posted: November 02, 2007 at 11:52 PM / IP Logged

I have 12 gauge wires for positive and ground running from my rear power and ground distro blocks in the back by my amps to my headunit. I have not and ounce of alternator noise. Everything must be ground and powered at the same point.

i am an idiot

Platinum - Posts: 13,667

This member consistently provides reliable information

Joined: September 21, 2006

Location: Louisiana, United States

Posted: November 03, 2007 at 6:53 AM / IP Logged

Don't cut your cigarette lighter plug. I am sure that YOU know that there is a circuit board in it that reduces the 12 volts of the lighter to the 5 volts that your unit needs.

The noise is being caused by a ground loop. A ground loop isolator will fix your problem. Yes you can use a small wire 18 Ga. or so to connect amp to radio but this will not fix your problem. Remember when you install the Isolator, there is an input and an output on the device. If you install it backwards it will cut the bass response to less than half.

The laptop had no noise because it was probably running on the battery. No chance for a ground loop there.

csnut18

Copper - Posts: 196

Joined: January 27, 2007

Location: United States

Posted: November 03, 2007 at 12:59 PM / IP Logged

Don't they sell a hardwire kit for your xm radio. I know I have seen it. Get that and just wire it to the same power and ground as your radio.

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