If you're shivering in your rig and trying to figure out an atwood hydro flame furnace how to turn on, don't worry—it's usually just a couple of simple steps once you know what to look for. Most of the time, these units are pretty reliable, but when they decide to be stubborn, it usually happens right when the temperature drops below freezing.
Let's walk through the process of getting that heat flowing so you can get back to being comfortable. Whether you have an older model or a newer DSI (Direct Spark Ignition) unit, the basics are mostly the same.
Make Sure You Have the Essentials Ready
Before you even touch the thermostat, you've got to make sure the furnace actually has what it needs to run. These furnaces are "dual-fuel" in a sense—they need 12V DC power from your batteries (or converter) to run the blower fan and propane to create the heat.
First, check your propane tanks. It sounds obvious, but you'd be surprised how many times a "broken" furnace is just an empty tank or a valve that got bumped shut. If you just swapped a tank, there might be air in the lines. I usually like to light a burner on the stove for a minute just to pull the gas through the pipes and make sure the pressure is steady.
Second, check your battery levels. If your voltage is too low, the fan might spin, but it won't spin fast enough to engage the "sail switch" (more on that later). If that switch doesn't click, the furnace won't even try to ignite the gas for safety reasons. If you're plugged into shore power, you're likely fine, but if you're boondocking, keep an eye on those levels.
Setting the Thermostat Properly
Once you know you have gas and juice, head over to your thermostat. RV thermostats come in all shapes and sizes—some are old-school sliders, and some are fancy digital touchscreens.
If you have an older analog thermostat, make sure the small switch on the top or bottom is clicked over to "Heat." Sometimes those switches are stiff, so give it a good push. Then, move the temperature slider to a setting well above the current room temperature. You should hear a faint click from the thermostat itself.
For digital ones, cycle through the "Mode" button until it says "Heat." Make sure the fan setting is on "Auto" rather than "High" or "Low" unless you specifically want the AC fan to run simultaneously (which most people don't). Once you bump the temp up, there's usually a 15-to-30-second delay before anything happens. Don't panic if it doesn't roar to life the second you touch the button.
The Ignition Sequence: What to Listen For
Understanding an atwood hydro flame furnace how to turn on is easier if you know what it's supposed to sound like. Once the thermostat calls for heat, the furnace starts its "purge cycle."
You'll hear the blower fan kick on first. This runs for about 15 to 20 seconds to clear out any unburnt gas from the combustion chamber. It's a safety feature—you definitely don't want a stray spark hitting a pocket of old gas.
After the purge, listen closely for a click-click-click sound. That's the DSI trying to light the burner. Once it catches, you'll hear a low "whoosh" sound, which is the flame igniting. Within a minute or so, the air coming out of your floor or wall vents should start feeling warm.
What if it's an Older Pilot Light Model?
If you're rocking a much older vintage rig, you might not have DSI. You might have to manually light a pilot. To do this, you'll usually need to remove the outer furnace door, find the gas valve, turn it to "Pilot," hold it down, and use a long lighter to hit the pilot burner. Once it stays lit, turn the knob to "On." However, most Hydro Flame units built in the last 30 years are automatic, so you likely won't have to deal with this.
Troubleshooting the "No-Start" Blues
Sometimes you do everything right and nothing. Or maybe the fan blows, but the air stays cold. If you're struggling with an atwood hydro flame furnace how to turn on and it's just not cooperating, here are the most common culprits.
The Infamous Sail Switch
This is the number one reason RV furnaces fail. The sail switch is a little plastic flap inside the furnace that detects airflow. If the fan is blowing fast enough, it pushes the "sail," which tells the circuit board it's safe to light the gas. If there's hair, dust, or a dead bug stuck in there, the switch won't close. No switch, no heat. Sometimes, just tapping on the furnace casing or blowing some compressed air into the intake can loosen it up.
Air in the Gas Lines
If your furnace tries to light (you hear the clicking) but fails three times, it will go into "lockout" mode. This usually happens if you've recently changed propane tanks. The furnace won't try again until you reset it. To reset, turn the thermostat completely off for a minute and then back on. You might have to do this a few times to bleed all the air out of the line until the gas finally reaches the burner.
The Reset Switch
Some Atwood models have a physical "On/Off" or "Reset" switch located on the unit itself. You usually have to remove the interior cabinet cover or the exterior access panel to see it. If this switch is flipped to "Off," the thermostat can't do a thing. Make sure it's set to "On" or "Reset."
Safety First: Don't Ignore the Smells
When you first turn on your furnace for the season, it's pretty normal to smell a little bit of "burnt dust." It's just the dust that settled on the heat exchanger over the summer burning off. It usually goes away after ten minutes.
However, if you smell raw propane (like rotten eggs), turn everything off immediately. Shut off the gas at the tanks and open your windows. You might have a leak or a fitting that rattled loose during your last road trip.
Also, always make sure your Carbon Monoxide (CO) detector has fresh batteries. Since the furnace burns fuel, you want to be 100% sure the exhaust is venting outside and not leaking into your living space. If your CO alarm goes off while the furnace is running, don't ignore it—get out and get the unit inspected.
Keeping it Running All Winter
Now that you've figured out an atwood hydro flame furnace how to turn on, a little maintenance goes a long way. Check your exterior vents for wasp nests or bird's nests; those little critters love the warmth and can block your exhaust, which is a major fire hazard.
Inside the rig, keep your return air vents clear. If you pile laundry or bags in front of the furnace intake, it can't "breathe," which leads to overheating and the furnace shutting itself down prematurely.
If you're still having trouble, it might be a bad circuit board or a faulty gas valve, at which point you might want to call in a pro. But in most cases, a full propane tank, a charged battery, and a clean sail switch are all you need to stay toasty. Enjoy the warmth!