Hot water tank fuse keeps blowing the fuse

[wjpatter]

Guys,
I've developed a problem recently that the 12 v, bayonet fuse for the hot water tank, keeps blowing when I transit. Very strange. I normally operate the tank on electric and all is well. I've never had problems stationary. Several time, not every time, I move the rig (300-40 miles) the switches, both gas and electric, are dead and I find the fuse blown. I replace the fuse and all is well. I've checked the control panel wiring for loose or broken wires and everything seen tight. I'm confident that I've got a loose wire somewhere making contact with ground and the fuse is doing what a fuse is supposed to do, open and protect the circuit. It has to be intermittent, or the fuse would pop as soon as I replace it - but it doesn't.

Does anyone have a wiring diagram or idea of how this is put together? Because I have a gas switch and an electric switch, I'm assuming that the control is transferred to the tank controller to make that selection. I'm assuming that is on the 12V system and that the 115VAC power goes directly to the hot water tank and is totally isolated from the control panel and the 12V system. Any ideas where I need to look next?

 

[WhittleBurner]

We had a relay go bad on ours, wasn't blowing fuses but you could see the melted wires and smell it as well. Check connections at the tank alsol. The relay sits next to the tank on the floor and was accessable on our 303. Don't think you'll have luck with wirting diagrams unless someone here has made one themselves of your model. GD does not usually share any wiring diagrams.

 

[jkwilson]

What brand and model is your water heater?

 

[dryfly]

Guys,
I've developed a problem recently that the 12 v, bayonet fuse for the hot water tank, keeps blowing when I transit. switch, I'm assuming that the control is transferred to the tank controller to make that selection.

Are you saying that you have the water heater on when traveling? If so, I agree it sounds like there may be a short to ground in the 12vdc line.

Next step would be determining if it's between the switch and heater or between the switch and +12vdc supply.

 

[wjpatter]

Are you saying that you have the water heater on when traveling? If so, I agree it sounds like there may be a short to ground in the 12vdc line.

Next step would be determining if it's between the switch and heater or between the switch and +12vdc supply.

I've had the electric switch on and blew a fuse and started turning the control off and have still blown the fuse. Whatever it is has to be intermittent and something associated with vibration and movement, or the fuse would blow when I replaced it. Thinking about that, the loose connection has to be in the control panel. I'm assuming the fuse is between the 12V bus and the switch. With the switch on, the short could be any when between the fuse and the heater but with the switch off, the short has to be between the fuse and the switch. I've looked at the control panel and didn't see anything loose or broken but maybe I need to revisit it. The spacing between all of the switch terminals are pretty close. Maybe a poor crimp where a couple of wire strands are loose, outside the crimp. Good idea, thanks for the response.

 

[jkwilson]

An old trick is to get a portable AM radio. Tune it to a space with no station and turn the volume up. With the radio close, jiggle wires and hardware of and around the water heater. If you move wires with sketch connections or a short, the sound in the radio will dramatically increase.

 

[wjpatter]

Latest update: Problem solved. I got a scary but key clue when the electric tank light went out when I pulled in the bedroom slide. The fuse was blown when I arrived at destination and this time, I drew a large spark when I put the replacement fuse in, blown, of course. I was able to get the camera into the space behind the slide and found both crimped lugs off and a lot of frayed wires. Regrettably, I had to cut a hole in the bottom of the slide to get access but was able to separate all wires to verify that it was the problem. I only found two crimps in the well. It isn't clear how Grand Design was able to wire things, but it may explain why I've always had trouble with the blue exterior slide lights.