Water heater 12vdc gas operation switch blows fuses

[Boomerweps]

When I tried to turn on my water heater using gas, after turning the interior switch (on the monitor panel), the monitor fuse immediately blows. I did not have any 15amp original capacity fuses, so I put a 20 amp in. Blew again, yes, I tried a third fuse with the same result. Where to test first? Didn't have a multimeter at camp, on the list to have in the TT. Also a good multi fuse pack.

[Mr. Dan]

Originally Posted by Boomerweps

When I tried to turn on my water heater using gas, after turning the interior switch (on the monitor panel), the monitor fuse immediately blows. I did not have any 15amp original capacity fuses, so I put a 20 amp in. Blew again, yes, I tried a third fuse with the same result. Where to test first? Didn't have a multimeter at camp, on the list to have in the TT. Also a good multi fuse pack.

The monitor fuse? Where do you find this monitor fuse?

[wmtire]

Originally Posted by Boomerweps

When I tried to turn on my water heater using gas, after turning the interior switch (on the monitor panel), the monitor fuse immediately blows. I did not have any 15amp original capacity fuses, so I put a 20 amp in. Blew again, yes, I tried a third fuse with the same result. Where to test first? Didn't have a multimeter at camp, on the list to have in the TT. Also a good multi fuse pack.

Forest River uses several different brand/make/models of water heaters. Can you please post a pic of yours and the panel switches. That will help tremendously in trying to troubleshoot your problem.

[babock]

Likely a pinched wire between the switch and the heater. Get the schematic for your heater and disconnect that lead from the control board. You can either leave the switch off or disconnect the wire from the switch. Then measure resistance to chassis ground. I that reads low ohms to ground, that wire is your issue.

Start with that since it is easy.

[Larry-NC]

Originally Posted by babock

Likely a pinched wire between the switch and the heater. Get the schematic for your heater and disconnect that lead from the control board. You can either leave the switch off or disconnect the wire from the switch. Then measure resistance to chassis ground. I that reads low ohms to ground, that wire is your issue.

Start with that since it is easy.

Since you (OP) are without a multimeter, disconnect the 12 volt line at the water heater. It should not blow a fuse, even with the switch on. If it does blow the fuse, it is a pinched wire between the switch and heater, as Babcock suggests. A pinched wire seems unlikely.

If it does not blow the fuse, the problem is at the heater. Not sure what model you have, but the key elements are:

• Solenoid (that shuts off the gas)
• Controller board (creates spark to ignite heater)
• 12v thermostat and wiring
• 12v overtemperature switch and wiring

First, do a thorough visual inspection of the wiring at the heater. Has any insulation burned through or chafed through? If not, disconnect one of these elements at a time and see if the fuse blows. Start with the easiest to reach.

For example, if you disconnect the gas flow solenoid, the heater won't ignite, but it will try. If the fuse doesn't blow, but you hear the sparking, you will know that the solenoid has gone bad.

Let us know what you find. This troubleshooting technique may cost you a couple of fuses, but it will get the job done.

[babock]

Originally Posted by Larry-NC

A pinched wire seems unlikely.

The reason I suggested that is that I helped someone with a similar problem on a brand new camper and the switch that turned it on in electric mode had a pinched wire.

[5picker]

After you post the make/model of the water heater and the monitor panel as requested, also answer this... did it ever work or is this something that just started happening?

[Boomerweps]

Water heater is a Suburban SW6DE, piping & silcon block any decent pictures of the heater stickers.
Monitor fuse is on the fuse panel, marked as such. It also powers the stovetop light & fan. Took pics of the panel & fuse box.
Now at home (where I posted the thread), have a few multimeters (added one into the TT . Thanks for the replies, will hopefully have time to get troubleshooting using the suggestions tomorrow, today was crazy busy. Had no wifi or phone reception at the CG. Also dug out the water heater manual, at least I now have a basic wiring diagram.

[Villagerjjm]

Look to see if there is a controller circuit installed near the water heater. Mine recently shorted out and I had to replace it. The symptoms I had were very similar to what you are describing. It will look like a plastic case mounted on a wall or the ceiling near the water heater and when you open it there will be a circuit board that will look like a little computer motherboard. Make sure you kill ALL power to the trailer before you tinker with it. It looks like there are some capacitors that can do damage to you.