Easy way to check if Sonar head unit is bad?

I am trying to determine if my Humminbird 859 ci HD is dead. I had a battery die last fall and I jumped the boat a number of times and after I returned from the river my boat smelled funny. Turns out my voltage regulator on the engine was melted out. The same trip this head unit had quit working. I know it had shut down due to low voltage a couple of times but then finally it just stayed off.

I have repaired the motor and also gotten a new battery – and when I check the voltage of the power cord to my unit I am getting 12.9 volts. So I know the unit is getting power – is there anything else I can check before I assume it is just done for? I know I could send it in but I’m not interested in putting more money into this than a fuse – I’d much rather upgrade the unit. Thoughts?

If it won’t power on and you know you got voltage to it that’s not a good symptom. I know of no internal fuses or anything else that can be checked. I’d say call HB customer service but they will just tell you to send it in. Given what you describe I’m guessing it’s cooked. Go upgrade and good luck!

Where did you check the voltage to the unit? Was it at the plug end that directly connects to the back of the unit or where you spliced the power in?

Jumping a battery with electronics hooked up can sometimes damage electronics. It could be a simple, inexpensive fix for Humminbird if the problem is in the head unit and they may give you a free estimate. The estimate may just cost you shipping to get it there.
On the other hand, it may just be a good time to upgrade.

Last time I check hummingbirds was around $300.00 flat rate to fix any unit if you sent it to them I’d put my money to a new unit

Thanks guys. I checked the volt reading at the connector to the back of the unit I was hoping to find nothing and then hunt for a fuse. And I also couldn’t find that they had any internal fuses. I’ll probably call just to double check anything else to try. There’s not a hard reset either.