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Suburban DSI water heater won’t light

I went through all the typical troubleshooting. I opened the gas line right st the water heater and it is flowing good and the gas works on the stove and the furnace. Hooked up to electricity the electric element heats up the water. The switch in the RV for the water heater is illuminated. It only works if the 110 breaker is on. I can not find a 12v fuse for the water heater, but I checked all fuses and they all look good. I can’t find another switch for the water heater. I put a multimeter on the 12v wires at the water heater and there is no power.

I just bought this and it is a cheap small RV. 2010 Heartland North Trail FX18. What am I supposed to be looking for here? I can’t figure out why no fuse appears to be for the water heater. I will directly power the water heater to test it, but it seems clear the reason it doesn’t work is that there is no 12v power to it. I have easy access to it so I have easy access to put the multimeter on the wires. 110 power only, no 12v power.

It makes no sense that no 12v fuse appears to be for the water heater.

There is no separate 12 volt fuse for the water heater. It is 120 or gas. The 12 volt circuitry is shared by the furnace and the fridge. maybe also the range hood. All these loads a very very small. There is a switch to turn the watwer heater on with gas. It will have a red light indicater. When you turn on the switch the red wight will come on then go out when the heater fires. If it does not light it will repeat this process 3 times. if it doesn't fire the red light will remain on. Find the switch and turn it on.
2011 Keystone Sprinter 323BHS. Retired Master Electrician. Retired Building Inspector.

All Motor Homes are RV's. All RV's are not Motor Homes.

OK, you DO have 2 switches for the Water Heater. You have found the 120 wall switch and if the light goes OUT when the 120 breaker is turned off that IS the 120 element wall switch. There is ANOTHER wall switch for the LP section(12 volt On and OFF) of the Water Heater. Usually, that switch is on the same panel all your Tank Monitors and water pump switch is located and will be labeled WH or LP. Doug

Explorer II
Explorer II
Badly missing some info here! You get the 12v red light ok if the "110v breaker is on."

But not if on battery and no shore power or gen? If so, that means your battery 12v is not reaching the DC fuse panel to run things, so no lights , no fans?

If you do have lights and fans but no water heater that is another story.

It appears you have a working converter to supply 12v when you have 120v, but not clear whether you have battery to the 12v whether any 120v or not.

That can mean the battery disconnect (if fitted) is open, or else the battery fuse (or DC circuit breaker) is blown down by the battery close to the pos post, or a dead battery.
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
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2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.