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ride98red · 01-16-2025, 09:22 AM

2022 Keystone Outback 328RL
Dometic Model DFMD35121
35k BTU

Brand new to the RV world. Purchased from Camping World (never again! Those people are thieves who practice lies and deceit with a smile on their face).
After bringing the trailer home, the freezing outside temps quickly revealed the need for the furnace as well as the fact that Camping World left water in the lines, (as well as left me with 2 dead 12v batteries making detaching the trailer real fun; left some of the 12v lights on in several inconspicuous areas thus contributing to the dead 12v batteries; failed to tighten the cap on the water pump filter thus allowing water to leak onto the floor; failed to have the trailer ready, 3 times, by not satisfying their "We Owe"...I digress), so now I have no heat, no water from any faucet, and frozen water in the toilet.

The symptoms from the heater were many and inconsistent. It almost seemed like the more I diagnosed, the worse things got. Eventually, the only thing that would happen is the blower would turn on followed by three cycles of fast clicking then the entire furnace would shut off. After some research, I discovered the "Sail Switch" and its associated failure potential.

After removing the sail switch, I discovered that it (the sail) was clean. (Found so many dog bones in the trailer so I was surprised to see it clean.) Evident that the techs at CW knew the heater wasn't working and made a half-hearted attempt to fix it. With the sail switch removed, I started testing continuity with my voltmeter.

Activating the switch with the voltmeter probes on each sail switch connector proved that the switch was faulty. BUT WAIT, there's more. Out of frustration I stared fidgeting intensely with the switch with the probes still attached. Suddenly, I heard a quick "beep." I couldn't believe it. I took a close look at the switch and found a small round hole with a pin. I pushed that pin out and the switch started to split in half. Grabbed a razor knife to pry the rest of the switch open.

With the switch open, I continued testing and quickly discovered that there was just enough "grit" INSIDE the switch that kept those delicate parts from moving freely and completely. So, I grabbed some PB Blaster and a can of compressed air. After a couple rounds of spraying, I tested the switch with the voltmeter and the switch worked perfectly!

NOTE: Another important aspect of this is the position of the sail switch sail. I am pretty sure it was originally in the forward most slot but it seemed to work better in the second slot - take a close look at the pictures.

After reassembling everything, the furnace has been working perfectly and it didn't cost me a dime, was easy to fix, and had heat back in the trailer within 2.5 hours.

The moral of the story: Never give up! This was a very easy fix and it turned a desperate situation around. And finally, never, ever purchase anything from Camping World!!