I just want to weigh in on this grounding issue with the hds touch screens. I have a HDS 7 gen2 touch and a HDS 12 gen2 touch I use in my boat. I have been attempting to convert them into ice fishing rigs but I have discovered the same issues matt-p was discussing. I hook up the power supply to my vexilar battery and the touch screen does not function. However, through A LOT of trail and error, I have discovered that if I touch the negative side on the battery with one hand and operate the touch screen with the other, it works flawlessly. Also, if i hold the accessory cables from the wiring harness in one hand and operate the touch screen with the other it works normal as well. This was consistent with multiple power supply harnesses and both my hds 7 and hds 12.

This baffled me because I have never had this issue when I have had it wired into my boat. So next I went and hooked it up to a car battery that was not in a vehicle, and again the same issue, touch screen not functioning. After all this, I went and hooked it up to a car battery that was in a car, and just like magic, it worked perfectly! So to me, it seems that a very substantial ground (like a vehicle or boat) is required in order for the touch screen to function normally.

This seems crazy to me since it really limits the capabilities of the hds touch units! I am going to be contacting Lowrance to discuss what I have found and see if they have any recommendations. Anyone else come up with a solution yet??