Originally Posted by BeeGee
It appears to be a Suburban D Model
What you have pictured is actually a Suburban SW DE model or maybe even a SW DEL model if you have two switches inside the RV for the water heater. The D stands for the Direct Spark Ignitor (DSI) that makes the sparks to ignite the propane and the E stands for the 120 volt AC Electric heating element.
That link I provided previously in post #2 explains the operation of both the SWDE and SWDEL models.
This water heater can be powered by propane or electricity to heat the water....or both at the same time.
The propane side works independent of the electric heating element side. There are two ECO hi-limit/thermostats, each controlling either the propane or the electric heating element. These are those TWO buttons underneath the rubber covers you said you pushed to reset. The left one is for the electric heating element and the right one is for the propane.
You said the electric heating works, so we are going to negate checking stuff for it.
Here is a schematic for a SWDE model. The difference between it and a SWDEL is negligible as far as the gas side is concerned so this should suffice.
As you see there aren't but really six things involved with the propane side. You first have a 12 volt DC switch inside the rv, then a junction box where wires are tied together, a ECO (Emergency Cut Off)hi-limit/thermostat, an electronic module board, a gas valve, and the electrode which makes the sparks to ignite the propane....to heat the water.
As explained in the previous operational link, when you turn on the DSI switch inside the RV, the thermostat senses the water tank wall temperature and if it's cold enough to need to be heated then allows 12 volt DC power thru to the electronic module board, which then allows power to the gas control valve and electrode ...... which then the gas control module allows propane to flow and the electrode ignites the propane.
It does this in a cycle. Once the inside DSI switch is turned on, this starts the first cycle. If after a few attempts by the electrode to ignite the propane fails, then the system shuts off (so propane is just not free flowing unlit). It will wait a few seconds, then attempt a second and even a third cycle if needed. You can usually hear a rapid clicking as the electrode is making the sparks.
Usually, After a third failed attempt/cycle to light the propane, the system goes into a lockout mode and no further attempts to light the propane will occur, since there is probably a lot of excess propane floating around at this point, which can be dangerous. Your DSI fault light (or reset light) will now illuminate full time that is beside the DSI switch inside your RV. This tells you that the propane failed to ignite and there is a fault somewhere and the system needs to be reset.
To reset this third strike lockout, you have to turn off the DSI switch inside your RV, wait a few seconds and turn it back on...which starts the whole 3 strike cycle again. You don't want to just do this haphazardly in case there is excess propane floating around.
Now if you do also have the electric heating element on at the same time, and the electric element is keeping the water temp heated, then the thermostat for the DSI will not sense any need for heat (since the water is already heated) and thus not allow the propane to turn on (as it's not needed) since the electric heating element is maintaining the heated water.
This post is running long and I will continue in another for what to troubleshoot easily. I just wanted you to get an understanding of the process and what items can be wrong that is keeping the propane side from operating correct.
If you turn off the electric heating element, to thus let the water cool down enough (it may take a while for the temp to fall enough) for the thermostat to call for heat on the propane side, does the fault light stay on after the three cycles? You may need to test this, as this also gives a sign where to troubleshoot....which can be something real easy. Do you hear the electrode clicking too when turning on the DSI switch?
Also before we go too technical, are you handy with a multimeter?
The easiest things to check at this point is to make sure the wires/connections are firm at the gas control valve and electrode.