Water Heater Info (How I fixed my SW6DE)!!!

I fixed my Suburban SW6DE propane water heater!!!

This just relates to the propane firing portion of the water heater (I have never had my TM plugged into a 120 VAC plug yet so I do not know if any of that stuff works).

As some of the previous posts have indicated, there is a rectangle plastic cover with two rubber plugs (each about the size of a quarter) attached to the outside wall of the water heater. It is screwed on with two sheet metal screws. Under this black plastic cover (see photo) is two independent thermostat modules and each thermostat module has essentially two integral thermostats and a reset switch for one of the functions of the module. Each thermostat module is attached to the side of the water heater tank with one small 3/8 hex head nut. The thermostats must be attached tightly against the water tank because they measure the temperature of the outside surface of the metal water tank.

One thermostat module (the one on the right side with the two red wires connected to it) is for the propane auto ignition system and the other module (the one on the left with the two black wires) is the module that works in conjunction with the 120 VAC heater element.

I imagine each module is essentially the same and they operate in the same manner. Each module has a non-adjustable 130 degree F temperature thermostat that is essentially a thermo switch that closes when the temperature is colder than 100 F and it opens up the circuit when the temperature gets to 130F or above. How it does this I cannot really tell by looking at it from the outside but that is what I gather it (they) do.

Also included with this module is the “ECO Switch” (however the service manual also calls this the high temperature limit switch) and this is a safety thermo switch that will open up the circuit by popping the little ceramic button out when the temperature gets above 180 F. The system will no longer work as long as that button is popped out.

When my water heater stopped working I naturally pushed in on the two rubber plugs and could not feel outward dimple of feel any “click” of movement. Then I checked the fuses at the Power Center.

I continued troubleshooting the system and I removed the PC Board Assembly from the side wall of the inside of the kitchen sink cabinet and tried to see if 12 VDC power was getting to the red wire of the PC Board and discovered that there was no power to this lead. I was however getting power downstream from the Heater ON/OFF switch in the System Monitor and I followed that red wire along the side of the water heater toward the street side of the trailer and then it disappeared between the water heater and the side wall.

I went outside and removed the plastic cover and found the two red wires connected to the right side thermostat module. One wire was powered with 12 VDC and the other wire was dead so I determined that the 100 F low temp “turn on” switch was inoperative. I tapped on it with a screwdriver and it started to work. If that did not do the trick I was going to unplug the two black wires and appropriate that thermostat module for the propane ignition system.

I then went back inside and plugged the wire harness back into the PC Board and turned on the switch and the PC Board started humming and clicking as usual.

Anyhoo…here is how the system works. When you push the red water heater switch on System Monitor panel the switch closes and allows 12 VDC to flow downstream along the red wire to the one thermostat module. If the water is colder than 100 F and also below 130 F the power will continue to the ECO high temperature cutout switch. If the ECO had not felt 180 F or higher at some point then that thermo switch will be closes and the power will flow back into the trailer along the second red wire and go to the PC Board and the PC Board will be energized.

The PC Board will then allow power to leave the PC Board along the brown wire and it will go outside the trailer and connect to the two solenoids (I do not know why there are two solenoids but it appears they work together as a team). As power enters the solenoids the electromagnet will energize and open a valve and let propane flow through the orifice and mix with outside air and this mixture will flow toward the burner chamber located inside the water heater. The PC Board will also energize the big capacitor (see photo of PC Board with the cover removed) and attached to that capacitor is the thick reddish orange wire that goes outside to the igniter. The igniter will ignite the propane and air mixture and flame will light off.

Somehow the system can determine if the flame is burning (I think the igniter is the sensor that will change it’s continuity when it ges hot) and if the system sees that the flame went out it will light off the igniter again for three tries however it will implement a 15 second delay between each try so that the gas in the burner can dissipate. After the third unsuccessful try to light off the burner, the system will shut off gas flow by de-energizing the brown wire and it will also send 12 VDC power from the PC Board down the blue wire and this will flow back to the System Monitor and this 12 VDC signal will light the “Reset if indicator remains lit” red LED to tell you that the burner flame blew out.

There is also a green and yellow wire in the schematic. The green is some kind of ground but the yellow is a complete mystery.

When my water heater did not work I noticed that the red LED was not lit however the red light in the switch was lit. Had I already wrote this description and posted it on the TM Owners Forum I could have read it and learned that since my switch light was illuminated that indicated that the fuse in the Power Center was good and power was getting to the System Monitor. Then…since the red “Reset if indicator remains lit” LED was extinguished I could have determined that the PC Board was not powered because the red return wire the feeds the PC Board was not powered. Here was the tricky part…since the ECO button had not popped I assumed that either the wires feeding the PC Board was broken somewhere or that the PC Board was fried.

While looking around under the kitchen sink with a flashlight, I determined that the best way to trouble shoot the water heater would be to remove the screws that attach it to the outside of the trailer, use a putty knife to scratch the silicon bead that was used to seal the outside cover to the side of the trailer, and then slide the water heater out about 18 inches (or more) and rest it on a table or something the same height as the bottom of the opening outside the trailer. It looks like all of the PEX hoses and wires and even the gas line are long enough to allow the water heater to slide out a bit so you can get to it. (see picture of wire bundle running outboard to the street side wall and then some of the wires simply turn around and go back inward however the red, black, and brown wires continue outside to the outside water heater panel).

So tomorrow I will visit the RV parts store and buy a replacement thermostat module and also buy a replacement sacrificial anode while I am thinking about the water heater.

I hope this will help someone else!!!