Blowing 3 amp fuse

I have 80lb Minn Kota Maxxum and the transducer interference 3 amp fuse keeps blowing.
Put a new one in used it today with SI on and it blew within a minute could tell by the interference on the screen. Checked when I got home and it was blown.
I've always had problems with interference but separating the wires fixed it. Now I have SI and DI on the trolling motor the problems have returned the sonar is fine it's just when I use the trolling motor the DI and SI gets fuzzy.
I have never checked the fuse until last week and that's probably been my problem the whole time any ideas?

Do you have an on board charger?

You have grounding issues. That brown wire (fused 3A) is tied internally to the motor housing . This connection puts the motor housing at the ground potential of the sonar via the shield wire of the us2 cable.

To fix, I have to get into motor housing and see whats loose?
I have a 3 bank with 2 leads to troller an 1 to starting battery.

Has the housing been removed before for some reason? To check for a possible internal short : disconnect the US2 cable from the sonar, then with an ohm meter, check between the housing and the US2 cable shield, The shield is common to the metal knurled connector on the US2 cable. If your meter is digital, use the continuity tone position. It is hard to confirm a short on a digital meter. Opens and shorts tent to read the same. I use my Simpson 260 analog meter for this type troubleshooting. The 260 knows the difference between an open and short.

I am referring to inexpensive digital meters. Any noise drives them crazy.

Chances are you have some kind of connection between the batteries powering the fishfinder and the TM batteries. A noise reducing ground and some kinds of on-the-run chargers are common sources.

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Originally Posted by minnowhooker

To fix, I have to get into motor housing and see whats loose?
I have a 3 bank with 2 leads to troller an 1 to starting battery.

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I had the same problem with a new Fortrex, it would blow the fuse immediately. I checked voltage and continuity, mine was back feeding voltage through the ground and blowing the fuse. Someone suggested I call Jones TM and pick his brain. After describing what it was doing the first thing he asked me was "Do you have an on board charger?". I do have, an older three bank 15 amp from BPS, Mr Jones suggested that I unhook it from the starting battery and check the fuse at the head again. Honestly I was expecting to replace the board but this was something that was easy to check. After unhooking the charger from the starting battery mine no longer had the back feed and quit blowing fuses. On a follow up call Mr Jones said he'd seen this with some on board chargers and suggested a Min Kota digital charger.

My charger still works great so I unplug the TM while charging the batteries and then unhook the charger wires from the start battery before I go fishing. When it craps out I'll buy a new Minn Kota.

Too bad Minn Kota doesn't put these problem/fixes in the FAQs. It is a common problem. The fuse blows because of stray currents.

I have a Mk charger disconnected from starting battery and tried anyway, when I turned troller on the fuse blew.
I just have a cheap multi meter the kind with a needle not digital could not get continuity.
I bent the shaft once and had it repaired at Chestnut and Prince Lane. Sounds like it's in the housing?

Check to see if the fuse blows when the transducer cable is disconnected from the unit.

What caftan said will work and easier than scratching paint for a continuity measurement. The brown us2 wire is mounted close to the positive brush. I have been here before.

Disconnected the transducer cable and still blew a fuse when I turned troller on.......I'm down to one fuse

Quote:

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Originally Posted by minnowhooker

Disconnected the transducer cable and still blew a fuse when I turned troller on.......I'm down to one fuse

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I'd call John Jones at Jones Trolling Motor. He's a sponsor here and knows his stuff. http://www.jonestrollingmotor.com/ 870 773-3474

yep.

http://www.evin.nl/2008/interne%20li.../Chapter_3.pdf

The units (2) I worked on had previously been worked on by someone who screwed up the internal stuff. Can't remember exactly. I try not to work on them, but you do things for friends. Lots of folks work on these units (including some small repair centers) have limited electrical knowledge.

For that fuse to blow, something has to be wrong on the load side of the fuse.

I agree Cane Pole about the wire an I don't think I want to crack that motor case. I do want thank everyone for all their time an help this is a great site with people willing to share their time an knowledge.
I will give Mr Jones a call in the morning and see if he knows of an easy fix but it's looking like I'm going to end up taking it somewhere.
Again..................Thanks Everyone