Finding the right atwood 8940 iii dclp replacement parts is usually the first thing on your mind when the heater starts blowing cold air right as the sun goes down. It's one of those "only happens when you really need it" kind of situations that every RV owner dreads. If you've got an Atwood 8900-III series furnace, specifically the 8940 DC model, you know it's a workhorse, but like anything with moving parts and electrical components, it's going to need a little TLC eventually.
The good news is that even though Atwood was acquired by Dometic a few years back, most of the guts for these furnaces are still pretty easy to find. You don't necessarily have to replace the whole unit just because a five-dollar switch decided to give up the ghost. Let's dig into the parts that usually fail, how to spot the trouble, and what you should keep in your "just in case" bin.
The Usual Suspects: Most Common Replacement Parts
When an Atwood 8940 III DCLP stops working, it's usually one of three or four specific things. You'll hear the fan kick on, maybe a click-click-click of the ignitor, and then nothing but cold air. This is the furnace's way of saying it's unhappy.
The Sail Switch
This little piece of plastic and metal is probably the most frequent culprit. The sail switch's job is to make sure the blower fan is moving enough air to safely vent the exhaust before the furnace allows the gas valve to open. If the switch is stuck, dirty, or just worn out, the furnace won't fire.
Because RVs are small spaces, things like pet hair, dust bunnies, and even spider webs can get sucked into the intake and jam the sail switch. If you're looking for atwood 8940 iii dclp replacement parts, the sail switch is the cheapest and easiest place to start. It's a simple "plug and play" fix that solves about half of the "fan runs but no heat" problems.
The Ignitor and Electrode
If you can hear the furnace clicking but it never actually lights, your electrode might be the issue. Over time, the metal probe that creates the spark can get charred or bent out of shape. The gap between the probes has to be just right—usually about an eighth of an inch—for the spark to jump and light the propane. Sometimes you can just clean them with some fine sandpaper, but often it's better to just swap it out for a new one. It's a cheap part, and having a fresh spark makes a world of difference in how fast the furnace catches.
The Circuit Board (The Brains)
Now, if you aren't getting any life out of the unit at all, or if it's acting completely erratic, you might be looking at a bad ignition board. The older Atwood boards were somewhat notorious for failing due to moisture or vibration. The replacement boards these days, often made by companies like Dinosaur Electronics or Dometic themselves, are usually a bit more robust.
Replacing the board is a bit more expensive than a switch, but it's still way cheaper than a new furnace. Most of them have a diagnostic LED light on them now. If yours is acting up, look for a blinking light on the board—it'll usually flash a code that tells you exactly what's wrong, which saves a ton of time on guesswork.
Dealing with the Mechanical Side
It's not always about wires and sensors. Sometimes the mechanical parts of the 8940 III DCLP are what give out. These are the parts that make noise or simply stop moving.
The Blower Motor
If you turn the thermostat on and hear a screeching sound like a cat in a blender, your blower motor bearings are shot. The 8940 III DCLP uses a motor that drives two fans: one for the room air and one for the combustion air. Because it's doing double duty, the motor works hard.
Replacing the motor is a bit more involved because you have to pull the furnace out of its cabinet. It's a "bring it to the workbench" kind of job. When searching for this specific atwood 8940 iii dclp replacement parts component, make sure you match the voltage and the shaft size exactly, as there were a few variations over the years.
The Gas Valve and Solenoid
While it doesn't happen as often as a sail switch failure, the gas valve can eventually fail to open. You'll know this is the case if the ignitor is sparking like crazy but there's zero smell of propane and no "whoosh" of ignition. Usually, it's the solenoids on top of the valve that fail rather than the valve body itself. Some people just replace the solenoids, but often it's safer and easier to just replace the whole assembly to ensure you don't have any leaks.
Maintenance Tips to Avoid Constant Repairs
Nobody wants to spend their vacation digging around in a dark furnace cabinet with a flashlight. A little bit of preventative care can go a long way in making sure your atwood 8940 iii dclp replacement parts stay in the box and out of the furnace for as long as possible.
- Keep it Clean: Use a vacuum or compressed air to blow out the intake and exhaust vents at the start of every season. Mud daubers and wasps love to build nests in these tubes, which can block airflow and cause the furnace to overheat or the sail switch to fail.
- Check Your Volts: These furnaces are sensitive to low voltage. If your RV batteries are weak, the fan might not spin fast enough to trip the sail switch. Before you start buying parts, make sure you're getting a solid 12.5 to 13 volts to the unit.
- Filter Your Air: If your RV allows for it, make sure the return air area is clear of obstructions. I've seen people block their furnace intake with a pile of blankets or a dog bed, which causes the internal limit switch to trip because the unit can't breathe.
Where to Source Your Parts
When you're ready to buy, you've got a few options. Since Dometic took over, you'll often find these parts listed under Dometic part numbers even though they fit your Atwood 8940 III DCLP perfectly.
I usually check Amazon first just for the speed of shipping, especially if I'm already on the road. However, for specialized stuff like circuit boards, places like PPL Motor Homes or even eBay can be great resources for finding "New Old Stock" (NOS) parts that are exactly like the ones that came out of your rig.
Don't be afraid of "aftermarket" brands like Dinosaur Electronics for the circuit boards. A lot of seasoned RVers actually prefer them over the OEM parts because they tend to be built with slightly higher-quality components that handle the rough-and-tumble life of a moving vehicle a bit better.
Wrapping Things Up
Fixing a furnace isn't exactly a "fun" Saturday afternoon, but it's a lot better than shivering under three layers of blankets because the heater decided to retire. Most atwood 8940 iii dclp replacement parts are manageable for a DIYer with a basic set of tools and a little patience.
Just remember to turn off the propane and disconnect the power before you start poking around in there. Safety first—you don't want to turn a simple repair into a bigger problem. Once you get that new sail switch or electrode in, you'll hear that satisfying "whoosh" of the burner lighting up, and you can get back to actually enjoying your trip in the warmth. It's a great feeling of accomplishment when you fix it yourself, and your wallet will definitely thank you.