Servicing an Atwood Hydroflame Furnace - Fiberglass RV


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Old 04-23-2018, 01:05 PM   #1
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Servicing an Atwood Hydroflame Furnace

Specifically the Everest Star installed in most Bigfoot trailers.

I'm no expert, but aside from having once stayed at a Holiday Inn Express, I also pulled mine out, replaced a bunch of parts, put it back in and...eventually it worked.

The disclaimers: this post assumes you are comfortable working with electricity and propane, a couple of the most-likely-to-kill-you things in your camper. I don't claim to understand all the systems and how they work, but I've always been decent enough at taking parts out and replacing them with new ones.

For someone used to intelligent tinkering, with an understanding of propane lines and electricity and safety, this is pretty straightforward. For someone stumbling around with very little understanding...pretty dang dangerous. There's a lot you can mess up if you aren't careful. If you aren't comfortable, don't mess with it. Spend the money and let a pro do it, or find a friend of a friend or whatever who has the experience and let them help you.

I had a furnace issue recently so I decided to do a bit of a refurbish of mine, replacing the parts that kept coming up as likely-to-fail when I was trouble shooting and searching the internet, and are included in tune-up kits like this.

This will just be a "how to replace" guide for a few parts, in case someone is searching, and like me, found nothing online. My furnace was in great shape aside from some failing electronics. If you find a lot of corrosion/rust or anything, it's probably better to just replace the entire furnace.

Ok, with that out of the way:

The circuit board, limit switch, time delay relay, electrode and most gas-related parts can all be replaced without removing the furnace. The sail switch, a common failure, cannot. The motor also requires furnace removal.

Furnace removal:

Turn off the gas at the tanks, pull the furnace fuse at the power center. If either of these cause you trouble, go ahead and call it quits and bring it to a service technician

Other than a screwdriver, helpful tools are allen wrenches, adjustable crescent wrenches, and a good pair of wire crimpers

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Unhook the gas line to the furnace. Take out the front screws.

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The furnace is now held in only by the exhaust tube sticking in from the outside of the trailer. You can wiggle/pull it out slowly, just until you can see the wires on the opposite side from where the gas connects. Once you can see the wires, cut them. I left enough wire to be able to see what color matches up to what, since they're different.

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Now work the furnace all the way out. I think it's a good idea to plug the open gas line in the camper. I also covered the gas connection on the furnace.

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Then remove the air intake and exhaust stuff from the outside. Two screws, then the rest just pulls out.

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These don't need to come out for servicing, but you'll have a very hard time getting the furnace to line up with them when you try to put it back in. You'll want to install them after you get the furnace back in. I just found it easier to get the leverage I needed to separate them from the furnace by pulling on the furnace itself, rather than these exterior parts.
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Old 04-23-2018, 01:17 PM   #2
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Circuit Board

The circuit board is right up front. Two screws, two electrical connections. This can be done with the furnace still installed in the trailer.

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I replaced mine with this. Mine is a 1991 HF8012. Don't believe anything you read online (including this). Call Dinosaur and ask what board replaces yours.

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There are two posts attaching the board.
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Old 04-23-2018, 01:48 PM   #3
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Sail Switch/Motor

This part requires furnace removal.

The motor on older, HF8012 models is no longer available. They only sell them for HF8012II, and they apparently aren't compatible.

This gets a little more involved but is still very simple. You need to take this side cover off. Find the bolts holding it on, they're pretty obvious. Loosen the hose clamp and slide the hose off the motor assembly. Pull out the motor.

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See the sail switch? Take out the screws, pull out the switch. It's attached by a couple more screws. Pay attention to its orientation.

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Atwood told me the wrong circuit board model. Maybe the wrong sail switch model, too?...Looks different, but it works.

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While I was in there, I took a closer look at the motor. My fan made more metallic squeaky noises than I liked, so I took the blower fan off the motor and made sure everything was lined up well. This is where allen wrenches come in handy.

Put in the new sail switch and hook things back up. See the sail of the sail switch sticking out in there? That's how it catches the air the fan is moving. If there isn't enough air, it won't blow that switch closed. If the switch doesn't blow closed, electricity won't go to the ignitor and the furnace won't light.

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Slide the motor back in and get the screws back in. For the hose, it helps to take this cover off. Pay attention to how it's lined up. It's a little confusing to get back on, otherwise. Get the hose back on the fan/motor all the way and tighten the clamp.

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My motor no longer squeaks, but seems to vibrate more. Not sure if that's from how I put the motor back in the furnace, or how I put the furnace back in the trailer. I may pull it again and see if I can smooth things out, but it is better than before.
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Old 04-23-2018, 01:50 PM   #4
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I'll post some photos of the limit switch and time delay relay. They can also be done with the furnace installed. Just two screws each and a few electrical spade connections.

For this model furnace, a direct replacement time delay relay is not available, but Dynosaur Electronics makes one that fits. It looks very different, but it works.
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Old 04-23-2018, 02:12 PM   #5
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Furnace Installation

Slide the furnace back in most of the way. Using new electrical connectors, crimp the wires together, paying attention to which color goes to which. Slide the furnace in the rest of the way. Put the front screws back in. Hook up the gas line. Don't use pliers. You'll destroy the soft surface of the connection pretty quickly. Install the outside plate, then slide the vent tube back into the furnace from outside of the camper.

Here's what you're aiming for:
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Turn on the gas. Using soapy water or another form of propane detection, make sure there aren't leaks. The fittings need to be fairly tight.

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Install the fuse at the power center.

See if it works!
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Old 04-24-2018, 07:45 AM   #6
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Here’s the limit switch. Two screws, two wires.

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Time delay relay. Sorry I threw away the old one before I got a photo...it’ll have 6 wires sticking out for models like mine, but it's important to know that the switch will only have 4 posts. Two wires/connections are "piggy-backed" onto other wires attaching to the switch. It works.

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Circuit breaker.

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Old 04-24-2018, 09:54 AM   #7
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Nice write up. Good detail. Thanks for taking the time.

For what it's worth I have a 7900. It's operation was intermittent from day one. I finally found the problem. A cold solder joint on the control board, one of the transformer pins as I recall. My control board looks identical.
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Old 04-24-2018, 09:38 PM   #8
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It’s nice to have this kind of stuff. There are a lot of things I never would have done, like rebuilding my transfer case and other automotive stuff if it hadn’t been for tutorials like this.

That would be aggravating...

Seems like the same story with a lot of newer refrigerators. Control board is crap. Replace it with a good USA one and then everything (more or less) works great for years.

I don’t think my trailer was used much. So a lot of stuff that might have otherwise failed a decade ago is starting to act up on me.

I’d like to think these Atwood’s cost so much because they’re that much more reliable than Suburban...but probably just wishful thinking.
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Old 04-24-2018, 11:46 PM   #9
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I cannot make a suggestion on the vibration but the RV guys who checked something else on our unit said the furnace exhaust is blowing a lot of black smoke, it is going back into another service company who only works on Winnebago;s so were hoping he can fix it fast, this unit is soon to be brand new after all the repairs we have made to it.
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Old 04-25-2018, 07:35 AM   #10
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Some things are just nothing but trouble from the beginning. Lemon comes to mind.

My vibration is not bad, but is more than I remember before. Way less annoying than the squeak, but noticeable enough that I figure there’s room for improvement. If I take it out again the wires are all getting quick connectors so I don’t keep cutting them & losing length.
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