DSI fault

[TopFac]

My 2021 171RBXL has a propane only water heater.
It's working fine, cycling on and off like it should, but the dsi fault light remains on.
Any clues?

[wmtire]

Originally Posted by TopFac

My 2021 171RBXL has a propane only water heater.
It's working fine, cycling on and off like it should, but the dsi fault light remains on.
Any clues?

Could be a bad module board. Are you sure it's propane only?

What make of FR product exactly is your 171RBXL

[TopFac]

Yes, propane only.
2021 Forest River Salem Cruise Lite 171RBXL.
Ran the water heater model number and it's only propane.

[Mr. Dan]

Thread moved to Propane Systems sub-forum.

[wmtire]

Originally Posted by TopFac

Yes, propane only.
2021 Forest River Salem Cruise Lite 171RBXL.
Ran the water heater model number and it's only propane.

Great, and yes the specs for this RV do say it's gas only DSI.

Can you post a pic of the fault lamp that's on? I have a reason for asking this. Thanks

[TopFac]

Stand by Sir...

[TopFac]

Hope this works and you can view it.

[Oaklevel]

On our 2013 our light was the light on when then propane was on. Was like that the entire time we owned it. May have been wired wrong but I knew when the water heater was on.

[wmtire]

Originally Posted by TopFac

Hope this works and you can view it.

OK Thanks, I'll fix that pic orientation later and explain some things when I get home this evening.

You do have a lighted rocker switch, which some people have thought is the DSI fault lamp, but I see your actual fault lamp is also illuminated. It's usually one of three things. Stay tuned

P.S. You stated you looked up the model number of your water heater. Can you also share these details as it will help me explain the wiring schematic later. Thanks

[TopFac]

SIR!!!
The model number is SW6D,
Sir!!!

[cboss]

Originally Posted by TopFac

SIR!!!
The model number is SW6D,
Sir!!!

Thanks for your service!
You can drop the "Sirs" on the forum. We are proud of our Vets, and are a little more on the friendly side on the forum since our retirements vs talking to a DI!


You'll get answers to your DSI issue shortly.

[TopFac]

OoohRaah

[wmtire]

Originally Posted by TopFac

SIR!!!
The model number is SW6D,
Sir!!!

Fantastic, I was hoping you had the Suburban brand and not the Dometic. The SW6D confirms it's the Suburban brand.

OK, let's look at the schematic for the SW6D. It's pretty straight forward. Factory wiring from suburban is color coded as seen in the schematic(Red and Blue wires are the two wires concerning your problem). Field Wiring (which is provided by Forest River) can be any color scheme. The field wiring will be the 12 volt DC + wire coming to the panel switch and then to the junction box. The field wiring will also be the DSI lamps 12 volt DC + wiring from the junction box back to the DSI lamp in your panel, as well as the - wire there too. The schematic has it shown as light instead of DSI lamp so you don't get confused.

What is not shown in this schematic is that you have an illuminated rocker switch to the water heater/DSI so it may have another wire connected to it too. I edited your pic in post #7 above too to point out the illuminated DSI lamp/light on your panel.



Once you turn on the power/DSI switch to the water heater it sends 12 volts DC to to the junction box (located on the backside of the water heater itself), now via the red wire thru the thermostat assembly, to the module board (also located somewhere near the back of the water heater), the blue wire back to the junction box and back to the DSI lamp.

Normally the DSI lamp will ONLY illuminate while the module board (the electronic brains) is waiting for the propane to ignite OR if fails to light.

You are showing where yours is illuminating, even though the propane is igniting and going thru the heating sequence. (which it's not supposed to). The lamp is getting power from the module board to illuminate, but it also can be another problem, but it's rare and is a short somewhere.

We can go further in this and test for what may be wrong, but it will require you accessing the backside of the water heater, where the junction box and module board is.... and/or opening up the panel inside your RV where the switch and DSI lamp are. Are you game for this?

Post #26 at this link will show you where the junction box is on your water heater as well as what/where the module board is too

https://www.forestriverforums.com/fo...ml#post1906134

[TopFac]

Roger that Gunslinger!
I actually understand everything you said.
Tomorrow we're leaving for home and I'll dig into this in the driveway.
I'll consult you with problems.
Told the wife apparently you're the guy who invented this water heater.

[wmtire]

Originally Posted by TopFac

Roger that Gunslinger!
I actually understand everything you said.
Tomorrow we're leaving for home and I'll dig into this in the driveway.
I'll consult you with problems.
Told the wife apparently you're the guy who invented this water heater.

Didn't invent anything, but have stayed in a few Holiday Inn Expresses.


Whenever you get time and decide to troubleshoot, what we are going to try and ascertain is if there is something miswired. As I said the DSI fault lamp/light "should" only illuminate when it receives power from the module board. I am assuming that whenever you turn on the water heater rocker switch, the DSI lamp/light stays on the entire time? Can you confirm this?

However, since you have a lighted rocker switch inside the RV that turns the power ON/OFF, there exists a possibility that something is messed up there pertaining to the DSI lamp and maybe something is mis-wired behind the panel that when you turn on the ON/OFF switch, it is sending power directly to the fault lamp/light...instead of just to the module board.

There is also exists something is mis-wired at the junction box, again providing power directly to the light/lamp instead of it coming from the module board.

Then there could be just a messed up module board sending power to the lamp/light when it shouldn't be.

We can test for all this, if you are confident using a multimeter or even a simple lighted circuit tester like this will suffice.


https://www.harborfreight.com/automo...-pc-63612.html

[wmtire]

The first thing we want to check and is fairly easy IF you can gain easy access to the back of the water heater (you will have to find this access from inside the RV), is to see if the blue wire that comes out of the module board is receiving power regardless of the module board. This shouldn't happen and if it does, would cause the lamp/light to illuminate when it shouldn't.


At the module board, there is a push on connector that you can pull off to test this. Here is an internet pic of this harness/connector not connected to either the module board or the junction box. Notice the red and blue wires going to the connector. That is what we want to test for 12 volt DC power.









What we want to do, is disconnect the wire harness from the module board. Then turn on the water heater switch inside your RV. You will have 12 volt DC power when you put your test probe in the connector terminal to the red wire This is receiving power due to the switch being ON.


Now you want test to see if the connector terminal to the blue wire is getting 12 volt DC power. It should not be, since it should only get power from the module board...and you are disconnected from the board.

Also look inside the RV at the panel where the switches are. Is the fault lamp on....as it should not be since it should not be getting any power since the wire harness is disconnected from the module board. If this lamp/light is on, then that shows where we need to look next.

After the tests/confirmation...you can turn the water heater switch back off and reconnect your wire harness to the module board. Make sure the switch is definitely OFF before reconnecting the harness to the module board.

[wmtire]

One more thing just in case you are not already aware, when I looked at your make/model RV, it appears your water heater is at the back right corner of the RV. This would put the access to the backside of the water heater in the bottom of your bathroom cabinets.



You can look for a removable panel, or may possibly have removable floor inside the cabinets to gain access to get to the water heaters module board and junction box. You need to know this anyway, as your winterization bypass valves will be located there too, in case you use them.