Our travel trailer is equipped with a Suburban water heater model #SW6DEC. The first time out it had issues igniting (popping noises). We switched to electric and it operated fine. The dealer performed some adjustments and declared it fixed. The next time out it seemed to be operating on LPG, but the following morning there was no hot water and the DSI lamp was on. Again, we switched to electric and it operated fine. The dealer checked it out and stated all is working fine.
The problem is it only operates on LPG for about 8-12 hours. Understandably, the dealer isn’t testing it long enough to experience the issue. We called Suburban and were surprised to learn that they have no technical department. Any insight you can offer would be greatly appreciated. —Reese, 2022 Forest River Salem Hemisphere
This is one of the “gremlins” I wrote about a while back, something that doesn’t work out in the field but works fine at the dealership. There are a few things that you need to verify when it is not working.
Check shoreline power
First, are you plugged into shoreline power when it doesn’t work on LP? If not, I would look at the house batteries to determine the voltage available. If your batteries are sulfated, they do not hold a charge very long and if you are dry camping, there is no 120-volt and there is no charge from the converter to the batteries. You can test this by using a multimeter to verify the voltage at the batteries when it does not work.
The gremlin in this situation is you drive the trailer to the dealership to have them look at it and the tow vehicle alternator charges the house batteries. It gets to the dealership fully charged, they bring it inside to a climate-controlled service bay and have nothing else running to draw off the battery and it works fine. Or, they even plug it in and it works fine. One other thing you can do is plug the unit in at the campground or hook up a battery charger and see if the unit works. This will identify if it’s the battery.
Check LP pressure
The second item I would check is LP pressure. When it stops working, shut everything off that is running on LP, like the refrigerator and furnace. If it works, then you have isolated the pressure regulator from getting weak and not being able to supply enough LP pressure to the water heater. Again, the dealership is troubleshooting with nothing else running.
Temperature and altitude could be the reason
If it is still not working, identify what the temperature is and the altitude, as being higher up in the mountains means thinner air and a harder starting system. Does the water heater attempt to spark? If so, you should be able to hear and see by opening the exterior cover and looking at the spark ignitor. If it is sparking, then it is an LP issue, which could just be a mixture adjustment for the area you are in. The supply tube typically has an adjustment that moves and either opens or closes the air intake slots.
If it is cold outside when it does not work, it could be a wire that is either too small a gauge or getting weak, or it could be the module. Cold weather causes line loss, which I experienced in the winter one year during a training trip. It was 0 degrees and the furnace would not ignite. I had to run the engine and use the motor aid which was plumbed to the bedroom from the engine coolant. The next morning I called back to the techs at the factory, who stated it was too cold for the furnace due to the wiring. How dumb is that! There is not much you can do to verify this other than try to start it once the temperature gets warmer.
The basics of troubleshooting are:
Does it work on one mode and not the other? If yes, it is an issue with just the components of that, in which your case is the LP mode.
Does it attempt to light by having a spark? If yes, it is an LP supply issue. If not, it is a power issue. But if you have no spark attempt, the module board will not open the gas valve and will not spark. You should be able to verify 12-volt power at the module board.
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I had a very similar issue being described in Dave’s article above. My water heater quit working. Took it into the shop 3 or 4 times. Each time the tech said it was working fine. But when I got it home and parked the RV the water heater wouldn’t work on gas. So I got to it trying to find the cause. Opened the access door and sure enough it fired up. Closed the door and it quit working on gas. Opened and closed it several times watching the very same thing happen each time – gas side only, never tried the electric that I remember. Finally watched closely while the door closed and opened, at which point I saw the problem. With the door open the wire to the igniter was straight making contact. While closing the door the wire would hit it and bend to the side shutting off the heater. The wire had a short in it so when the techs worked on it the door was open and the shorted wire was making contact. Closing the door caused the wire to bend to the side disrupting the flow of electricity.
Smart man, good job!
Thanks, Dave! I enjoy reading your thoughtful, thorough, and patient responses. Thank you for sharing your knowledge with us!
Another thing to test. Turn on the burners on the stove and watch the flames. If they appear to be ‘dancing’ it’s a sign of low gas pressure. There was a recall on regulators made by Winn-Tec, used on many RV’s. They did not sustain constant pressure.
Have they tried turning it off 📴 and then back on? Why do they feel they need to leave it on all night? That’s a waste of propane.
Gee Dave just a simple twenty two step process and….it might not work. 😂