I have a 2012 Z520 with an hds12 at the console and an hds9 at the bow. When fishing the hds9 is perfect. When I'm moving across the lake, the hds9 at the bow will start flickering and shut off, and I'll have to power it up each time I stop to fish.

I admit it doesn't happen 100% of the time, but easily 90%. And I find it odd because my front graphs did the same on my 2010 Z520.

I checked the cables and they are snug and the tap into the power seems to be good. I have a feeling it's a voltage issue, but I'm the first to admit that I don't quite understand voltage and how it effects certain things.

Anyone have an idea what my problem could be?

In line fuse ? loose inside

I would try to power the front graph directly to the starting battery. This eliminates the issue the majority of the time.

I had the same problem and found that the wire that brought power had been cut and was cutting in and out. Replaced wire and everything is good.

I/E=R

Had the same issue. Had a loose wire. I would check your connections.

Had a similar problem and it was my batteries.

Sautered my connections and never had the problem again.

Soldered connections (without other mechanical constraint) aren't even allowed by ABYC standards. A crimped terminal connections is actually better.

The OP needs to look at the clues. The bow unit works fine when floating around, but starts getting flakey when he's moving on plane. About 99 out of 100 times, that says there is a connection issue that is affected by the movement and vibration of the boat on the water. When an outboard is running at RPM above idle, the boat's electrical system voltage is at its highest because the charging system has it jacked up. What he almost certainly has is a continuity problem (loose/bad connection or broken wire), not a "voltage" problem.

How to find the offending problem? Park the boat, run the bow unit, gain access to the wiring, start moving and wiggling the wire harness at the bow. When you get to a problem area, you'll cause the unit to do like it did on the water. Sometimes it's a crimp where the power is tapped that's not tight, as an example. Sometimes a wire that can flop in rough conditions that has moved back and forth so much that the strands of wire are broken but still touching inside the insulation, though not as common.

One last possibility: Have you considered that the HDS9 has an issue with an internal loose connection? It could be that the G forces from vibration when you run across the lake are causing the unit itself to have an issue. Do you have access to a different HDS 9 to try on your bow? An alternative is to take yours out of the bracket and bump it on the deck while running to see if it flakes out. Don't slam it, just give it some bumps like it might get out on the lake.

I had the same problem, The screen would flicker then shut off while running and would power back up fine when stopped. It ended up being 2 screws on one of the boards (that also act as a ground) inside the unit had come loose. Put the screws back in and tightened, haven't had a problem since.

I had that same problem even while fishing the front graph would go out. I had a voltage drop to the front from loose wires in the back. Check the connection from the battery to the bus bar on the transom, at least that is where mine is located.

All I can say is that a copper wire with an aluminum wire end is destined to fail if crimped.

I had the same problem and it ended up being my rocker switch was bad.

This!

I rewired both my graphs straight to the battery and it solved my problem. It was voltage drop.