Furnace Issue

[215Airhaus]

OK, gang, I have one for you. I was out for a shakedown trip the last couple of days. Prior to leaving I tested the rig systems, including the furnace. In the driveway I fired up the furnace with no problems. I will admit that we were still hooked up to shore power when I tested the system, but I don't think that should matter.
Now, when I was out in the field, dry camping, the furnace failed to fire. I turned on the system, set the temp, the fan went on, but it did not get hot, and then after about 15-20 seconds, the fan turned off. No heat.

What am I doing wrong here? Thank you for any and all help, folks.

[glcmranger]

Since it fired up while on shore power, I suspect your batteries. You need minimum of 12.2 battery power to ignite the furnace in order for the propane system to take over.

[aftermath]

The battery might be an issue. Has if fired back up when you are connected? If it is not firing, it could be your sail switch. This little gizzy opens when the fan comes on for safety reasons. Once it is open, the furnace will fire off. If it doesn't open, or is fouled with something, your furnace will act exactly like you described.

The good news is, this is an easy thing to check, clean and replace IF you can get to it. Mine is hidden way deep in the bowels of the furnace. I have to remove the furnace to get to it. Sheesh........

[215Airhaus]

Originally Posted by glcmranger

Since it fired up while on shore power, I suspect your batteries. You need minimum of 12.2 battery power to ignite the furnace in order for the propane system to take over.

Thanks, good call. Checked the batteries and we are good there. Plenty of juice even off shore power.

[215Airhaus]

Originally Posted by aftermath

The battery might be an issue. Has if fired back up when you are connected? If it is not firing, it could be your sail switch. This little gizzy opens when the fan comes on for safety reasons. Once it is open, the furnace will fire off. If it doesn't open, or is fouled with something, your furnace will act exactly like you described.

The good news is, this is an easy thing to check, clean and replace IF you can get to it. Mine is hidden way deep in the bowels of the furnace. I have to remove the furnace to get to it. Sheesh........

OK. We are back home, parked in the driveway, fairly level. when the furnace failed yesterday we were hitched up and not as level as we are now. I just tested the furnace. Unhooked from shore power. And, darn it, it worked. Now, money question, would being too far off level effect the performance of the sail switch?

[Steamy1]

My furnace was doing the same thing. I tried a suggestion that I had read about: when the fan goes on, stand outside by the exhaust vent. When you hear the igniter start clicking, place the palm of your hand on the vent for just a very brief moment to block the exhaust air for just a second.

I tried this and the furnace burner ignited. It has worked ever since doing this. It must have cleared something that was blocking the sail switch or some particles on the burner tube.

This is assuming that the LP supply line has been purged of air. I turn on one burner on the stove and use a lighter until it lights.

[215Airhaus]

Originally Posted by Steamy1

My furnace was doing the same thing. I tried a suggestion that I had read about: when the fan goes on, stand outside by the exhaust vent. When you hear the igniter start clicking, place the palm of your hand on the vent for just a very brief moment to block the exhaust air for just a second.

I tried this and the furnace burner ignited. It has worked ever since doing this. It must have cleared something that was blocking the sail switch or some particles on the burner tube.

This is assuming that the LP supply line has been purged of air. I turn on one burner on the stove and use a lighter until it lights.

Also, it was incredibly windy where we were camped.

[PB_NB]

+1 on the sail switch!

I went around in circles when ours stopped working. I tried a bunch of things and sometimes it would work and then it would stop at the next spot. Very frustrating.

I was about to order a new main board but pulled the sail switch and found a ball of fuzz on the switch. Once the fuzz was removed and sail switch back in, it has been perfect!

[Tim A.]

Originally Posted by 215Airhaus

OK. We are back home, parked in the driveway, fairly level. when the furnace failed yesterday we were hitched up and not as level as we are now. I just tested the furnace. Unhooked from shore power. And, darn it, it worked. Now, money question, would being too far off level effect the performance of the sail switch?

Having replaced the sail switch in our furnace more than once, when it is now responsible for our furnace not lighting, I just bang on the side of the furnace where the switch is located. Doing so seems to unstick the switch and the furnace works again. Perhaps driving home vibrated your switch enough to free it up.

Tim

[aftermath]

Originally Posted by 215Airhaus

... Now, money question, would being too far off level effect the performance of the sail switch?

Boy, I doubt that level would have an issue. When the fan kicks on the air flows through the combustion chamber, clearing it of any residual propane as one of the requirements. This sail switch is a flimsy piece of metal easily moved by the air from the fan. If it was off level, I doubt it would cause it to stay closed.

This falls into one of those "magic" happenings with my trailer. Tap on this, shake that, stand next to the exhaust, put your hand over the opening, turn things off, turn things back on.....and the gods watching just might "fix" it. I have been there and have done all those kinds of things and....sometimes it works. Take a look at YouTube at "sail switch" and you will see some interesting video of clogged sail switches. I think some of these situations can correct themselves but that is just another "magic" step for me.

[JeffKim]

Our furnace went out and I tried everything and eventually let JC figure it out. I did replace the sail switch and they are pretty cheap and easy. I will add my vote to give this a try.

Other than that, I did find the grounding wire was not attached very well which would cause the blower to go out, but you don't have that problem.

[Two Chicks]

We had a problem with the furnace a while back. I took the front of it apart and noticed a flashing red light inside. Upon further inspection, I found a sticker that was not easy to notice. I took a pic and this is the info on the sticker:


IGNITION CONTROL DIAGNOSTICS

Number of Flashes ==> Diagnostic Information

1 w/ 3 sec. pause ==> Air Flow / Limit Fault

2 w/ 3 sec. pause ==> Flame Sense Fault

3 w/ 3 sec. pause ==> Ignition Lockout Fault

Steady on, no Flashing ==> Internal Control Failure


Turn off all of the lights in the camper and look inside the furnace. It helped us.

[David in Lex]

Check the sail switch in the furnace unit (accessible via outside panel). These can fail unexpectedly. Easy to replace.

[KK4YZ]

Originally Posted by 215Airhaus

OK, gang, I have one for you. I was out for a shakedown trip the last couple of days. Prior to leaving I tested the rig systems, including the furnace. In the driveway I fired up the furnace with no problems. I will admit that we were still hooked up to shore power when I tested the system, but I don't think that should matter.
Now, when I was out in the field, dry camping, the furnace failed to fire. I turned on the system, set the temp, the fan went on, but it did not get hot, and then after about 15-20 seconds, the fan turned off. No heat.

What am I doing wrong here? Thank you for any and all help, folks.

Sail switch. Before the furnace will fire up the gas, it checks to see if there’s airflow via the sail switch. It’s a safety feature. You can pull it and clean it if needed or replace it,

[mayco]

https://myrvworks.com/wp-content/upl...ace-Manual.pdf

Before you start throwing parts at it (the poke and hope method) Read through the start sequence and troubleshooting sections in that link. The sail switch is only one of several items that could be giving you fits. Seriously, read through that link, it will give you a handle on how these units work. It’s not real technical or hard to understand. It’s the best way to start your repair and cut your frustration level down.
On my furnace, you have to pull the unit out in order to get to the sail switch. It depends on what model furnace you have and what model Airstream you have. As usual with Airstreams, what sounds like a quick and easy repair usually ends up being a real pain in the rear.
Good luck, do your reading, and you’ll get it solved. Just don’t start throwing parts at it before you understand what it does and how it works.
Mike

[Hilljeman]

I have a 2022 GT 25FB twin. 100% of the time when I thought my furnace had a problem it was nothing more than LP gas, not getting to the furnace. What I did on these occasions, was light the stove, which took several seconds, to ensure that gas was making it that far. Then I tried the furnace and it always worked.

[Steamy1]

I hope this is on topic for this thread, since it contains several references to replacement of the sail switch, I thought it would be appropriate to comment on my experience with my efforts to replace it in our 2015 23FB. The Atwood furnace model according to the label on the blower casing is a AFSD20111. According to Dometic website support and the parts detail for this model, the sail switch part number is 31093. After much digging around, it seems like this has been replaced by 31094.
To be certain, I contacted Dometic support for assistance. They asked me to send pictures of the labels including the serial number which they could not verify. It is a "curved" bladed model, not the straight blade.

After several days, they responded with: "I was able to speak to a supervisor about the sail switch you are needing for your furnace. Unfortunately, the company that Dometic used to make these sail switches is no longer making them. The sail switch you need is no longer available. This means that it would require a complete replacement of the furnace. If you are the first owner of the furnace and within 2 years from your original date of purchase, then this would be covered under manufacturing warranty. If not, then you would have to replace the furnace and pay out of pocket for the replacement."

So according to Dometic, I am unable to order an OEM part for a product that is only seven years old. Seems outrageous for a major worldwide manufacturer.

I was able to find one at Airstream Adventures in Idaho (thanks Melissa!).

So it you need one of these you will have to order knockoffs on Amazon, which may or may not meet specs, or try to locate an OEM with some supplier that may have some still around.

I went ahead and replaced the igniter board with a Dinosaur and the limit switch and have a spare sail switch and ceramic igniter on hand.