Garmin 590 GPS on a 2015 Goldwing level 3

[RadBikerBuck]

Just purchased a 2015 level 3 goldwing. Had to get the level 3 for the ABS system, but it also came with Honda factory G.P.S. and for several reasons I do not like the factory G.P.S. I purchased a
Garmin zumo 590 to mount on the bike and ordered from Sierra Electronics their GPS interface for Goldwings (Hollsco). Now my dilemma, there is a constant low background hiss when XM radio is
on (not loud just aggravating), This interface unit has a ground loop isolator and it is supposed not to allow this to happen. I would sincerely appreciate any help on this item. Thank you for your time and consideration.

[WingAdmin]

Just purchased a 2015 level 3 goldwing. Had to get the level 3 for the ABS system, but it also came with Honda factory G.P.S. and for several reasons I do not like the factory G.P.S. I purchased a
Garmin zumo 590 to mount on the bike and ordered from Sierra Electronics their GPS interface for Goldwings (Hollsco). Now my dilemma, there is a constant low background hiss when XM radio is
on (not loud just aggravating), This interface unit has a ground loop isolator and it is supposed not to allow this to happen. I would sincerely appreciate any help on this item. Thank you for your time and consideration.

Does the hiss go away when the XM radio is turned off? What about when the XM radio is on, but the intercom is turned off? Lastly, if you unplug the GPS Input from the Zumo, does the hiss go away?

[RadBikerBuck]

Hiss is still there with XM is off, Hiss go's away when Zumo is unplugged from the Hollsco Group GPS input system.

[WingAdmin]

It sounds like the Zumo is sending digital hash (noise) out its audio line. I would get a ferrite choke - Radio Shack has them, or Amazon:

Amazon: http://www.amazon.com/RadioShack-Snap-T ... ingdocs-20

This one is from Mouser: http://www.mouser.com/ProductDetail/TDK ... id=2255132

Put as many loops of the audio lead as possible through the choke, as close as possible to the Zumo. With any luck, that will kill the noise coming from the Zumo.