Dear Dave,
I have a 2003 Forest River Sunseeker Class C motorhome. I bought this recently and don’t know much about all these things, so I read your column diligently. Recently it was 23° outside and I had trouble getting the furnace to start. Once it started it was incredibly noisy. Is something wrong, or is this just the way the furnace is on an old RV? Thank you. —Shanti
Dear Shanti,
To provide more specific troubleshooting information I need to know the make and model of your furnace. However, there are a few generic troubleshooting items you can look at.
First, does this occur while you are connected to shoreline power or dry camping? If you are dry camping, then I would start by looking at the battery to see if it’s fully charged or sulfated. Hooking up a battery booster would determine this right away.
Next, I would look at getting a new thermostat as these are very poorly made and usually have inferior wiring. That could be the issue during cold temperatures. I remember not being able to start the furnace while traveling for Winnebago in 10 degree temperatures. When I called back to tech support they told me it was too cold for the furnace to light! They eventually fixed the problem with proper gauge wiring. You might even want to replace the thermostat with a newer model.
Altitude could be an issue
Another issue could be altitude, as the mixture would be difficult to light. If you are in the mountains when this happens I would recommend contacting the Original Equipment Manufacturer (OEM) to see if they have an optional orifice for higher altitudes.
Have your furnace properly serviced. That means they would take the unit out and clean the burner assembly, intake, and manifold. All this is inside the furnace and can affect the airflow and fuel ratio. At this time, they would also check the motor and fan—which are probably what is making the noise.
It also could be bearings in the motor or a broken piece of the fan or squirrel cage. The unit should not be that noisy. This is something you might be able to inspect yourself. However, you would need to remove the unit and take it apart to do so, and need to determine your level of confidence.
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.
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I saw a YouTube piece where a fellow discovered the noise was caused by a mummified mouse in the squirrel cage.
If this is the first RV and he is use to the sound of the S&B furnace’s quiet sound just the sound of a RV furnace is loud because it’s right next to you. I know the first time I turned on a RV furnace I thought it was coming out of its mounting hole.
We once had a problem with our fridge not wanting to stay lit at high altitude – 7500 feet. We contacted Norcold and their tech support said we should move to a lower altitude. That was how they offered a ‘solution’. The furnace worked fine.
Or, if it’s snowy at 7500 feet, just move the stuff in your fridge outside. There. That’s about as good as Norcold telling you to move to a lower altitude. Take care, Tommy, and have a great day. 😀 –Diane
Just now in the process of replacing the motor in my 2000 Lance camper Atwood Hydroflame furnace. Hard to start and noisy because motor bearings were rough and grinding. This caused the motor to run slower which didn’t allow the fan to activate the ‘sail’ switch. Bad bearings also caused all the noise. (Did not have to remove the entire heater .. YouTube videos were great!)
You forgot to mention that if the battery is cold it will provide a lower voltage even if fully charged. With the furnace blower receiving lower voltage, the motor spins more slowly, both from the low voltage and thicker oil in the bearings and will not deliver enough air to close the sail switch.