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Old 02-16-2011, 06:01 AM   #1
Rivet Master
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2005 19' Safari
1968 24' Tradewind
Rural , Delaware
Join Date: Jun 2005
Posts: 1,476
Need advice on furnace.

The Bambi goes to the Airstream authorized repair facility for repairs in a few days under our extended warranty. One of the items on the list is the Hydro Flame/Atwood 7920-II furnace. It's not igniting. A few months back, it started to fail sporadically, then progressively got worse.

We called our AS dealership (former, now just parts/repairs) where we bought the trailer for an appointment, and was told the wait time was over 2 months. Since we were about to leave on our cross country trip in a few weeks, this wouldn't work for us so we called an RV shop just a couple miles down the road and they took us in that day. They fixed it the same day at a very reasonable price. They said the burner orifice was clogged by some debris. But the fix only lasted a couple of weeks and reverted back to the same problem. By then, we were on the road. Since we were winterized and the furnace would occasionally come on, and we really didn't have much of an agenda, we headed south and figured if it got bad enough, we would have it fixed on the way to wherever. We traveled away from the cold weather. Sometimes it was quite an adventure. Worst case scenario, we had a small electric heater and the Honda 2000 generator. Anyway, here are the symptoms...

- It was a progressive problem, gradually getting worse.
- I can very clearly hear the ignitor sparking (three times before it goes into ignition lockout-blinks three times).
- Occasionally, I can hear an arching/snapping sound when it is trying to ignite, which wasn't there before the first repair.
- I find this one odd... When it is attempting to ignite, the LP alarm (Protechtor-Series 2001) light, which normally blinks about every 4 seconds, comes on solid green-sometimes solid yellow, and occasionally turns red and chirps. This alarm behaved erratically from day one, but I understand this is somewhat normal behavior for this model.
- All other gas appliances work just fine.
- I can smell some propane outside at the exhaust when it is attempting ignition.

Since propane furnace repair is slightly above my pay grade, I did some minor diagnostics:

- I pulled the circuit board and checked the integrity of the connections. All was good.
- I learned a low battery can cause ignition problems, so I checked the battery voltage, both at the solar control panel and at the battery. Both were 13.78 volts when connected to shore power, and 12.5 volts when unconnected and the battery switch in storage mode.
- The interior/exterior lights are steady, and do not blink or dim when another appliance is turned on (except the heat pump).
- When the weather was good, we did a lot of boondocking and overnight parking without hookups. On most nights, after using the lights liberally, and the furnace occasionally coming on (1-4 times), the batteries were usually at 85-90% in the morning. Since the furnace wasn't working and there was no real way to do a practical battery test under a steady load, this still leads me to believe the two original AGM batteries are still going strong.
- We use the AS a lot, extensively during the season, and as much as we can during the winter (between blizzards), to the point where we sometimes don't winterize, just leave the furnace on, so it doesn't sit around in the yard much. This probably explains why it's showing signs of wear .

If you got this far, thanks for having the patience to read this. and any insight would be much appreciated.
2005 Bambi
1968 Trade Wind
2007 Ford F250 4x4 Crew
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Old 02-16-2011, 06:45 AM   #2
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1972 31' Sovereign
Lexington , Minnesota
Join Date: Feb 2009
Posts: 3,803
I would suspect more debris in the burner, or the ignitor is not aligned correctly. The ignitor clicking 3 times is normal. The arcing/snapping sound is not. That could mean the ignitor lit either some stray gas, or the flame popped back up the burner to the orifice. Neither situation is good. Since you can smell propane, the gas valve is probably opening ok, and the ignitor is trying to light the burner ok, but something is preventing the burner from lighting correctly. My biggest concern after reading your post is that gas is leaking outside the burner instead of staying in it.

If you have the skills, pull the furnace out and check all the connections around the burner assembly. Check the alignment of the ignitor as well. It should spark onto the burner. If you don't have the skills or tools, or are not comfortable doing that, please bring it in to be checked before trying to use it again.

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Old 02-16-2011, 07:28 AM   #3
Rivet Master
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2005 19' Safari
1968 24' Tradewind
Rural , Delaware
Join Date: Jun 2005
Posts: 1,476
Thanks, Chris.

The sound is more like an electrical spark than ignited gas. The gas smell is from outside at the exhaust port when the blower is on. There is no propane odor inside the camper. I'll be leaving the LP work up to the pros. I just didn't want to get to the shop and have them say it's a battery problem. The furnace behaves the same on shore power, and when it's not hooked up.

Thanks again.
2005 Bambi
1968 Trade Wind
2007 Ford F250 4x4 Crew
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Old 02-16-2011, 08:18 AM   #4
2 Rivet Member
2008 19' Safari SE
satellite beach , Florida
Join Date: Feb 2009
Posts: 35
I have a 2008 Bambi which had the same problem and symptoms. The AS dealer I went to for service miss diagnosed the problem and replaced an expensive part, under warranty ( 10 days at the dealership ) which didn't fix the intermittent problem. I called Atwood and they recommended a service center which diagnosed the problem in 10 minutes. It was the igniter electrode. It had a hairline crack. No problems since this repair, also done under warranty. I highly recommend calling Atwood for a local service center.
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Old 05-28-2011, 11:10 AM   #5
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2015 23' FB International
2007 19' International CCD
Steamboat Springs , Colorado
Join Date: Nov 2007
Posts: 860
Thought I would pass along my recent experience with my furnace.

We have a 2007 19' Bambi, with an Atwood 7916ii furnace. On our first trip of the season to Utah, I could not get the furnace to ignite. The blower would come on, and I could hear the electrode snapping, but no ignition. I also noticed a spark from the connection side of the electrode arcing to the furnace metal.

Also, the LP detector would start chirping.


1. Replaced the LP detector
2. Removed the electrode and noticed a small crack in the porcelain. Ordered a new one, with a gasket, from PPL and replaced. Also checked the gas line connections.
3. When the furnace was turned on, it immediately ignited. It seemed like a success, but jubilation was premature.
4. The next day, tried to start the furnace, and it would not ignite.
5. After conferring with my friend, I decided to replace the circuit board with a Dinosaur (Fan 50) brand purchased from Randy at Best Converters.
6. Installed the new board. Blower would start, followed by the electrode providing the spark, but no ignition.
7. Removed the furnace, checked the sail switch and used compressed air to clean out the fan blades, ducts, etc.
8. Re-installed everything, and cycled. No ignition.

By this point, I was resolved to making the 150 mile trip to Denver and taking it to a service center. I had reached the apex of my desire and capacity to mess with it.

However, late last night I rooted around the forum, and someone mentioned trying to briefly apply back pressure by placing your palm over the exhaust outlet when the electrode is sparking. I raised the thermostat, the fan started, I then went outside and placed my palm over the exhaust outlet, the electrode sparked, and the furnace ignited! And no chirping with the new detector connected.

I have been letting it cycle on and off all day, and it seems to be working. I will continue to check it over the weekend.

So what was the initial problem? I wish I knew. Maybe there was a small particle of debris or soot blocking the orifice, and the brief compression of air created enough oxygen for ignition to occur and blow it out. It is a mystery to me.

Many thanks to the poster for suggesting the hand-over-exhaust technique!

Now, if I can just track down the pin-hole leak coming from the frame of the FanTastic Vent….
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Old 05-28-2011, 03:47 PM   #6

2003 25' Classic
Zanadude Nebula , Milky Way
Join Date: Jun 2007
Posts: 17,787
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Look down that exhaust tube, make sure there are no mud-dauber nests in there....removed ours last season.

I now peep down the tube every so often.

"It is more wiser to ponder all things with diligent suspicion, than follow with blind assumption."
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