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Furnace Won't Ignite


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I've read some similar situations here in the forums, but my situation is different in that even plugged into shore power, the furnace won't ignite. The blower comes on after a few moments, but no ignition - just cold air. I've lit the stove burners and left them on, so there is LP flowing. Granted, I don't know how long it's been since the furnace was last used as the previous owners were both Floridians (as I am.) However, I travel and boondock extensively, so a heat would be fantastic.

Are there replaceable parts I should be looking at? It's a little dusty in there once the grille is off. I don't know much about coach powered stuff - should I disconnect the deep cycle battery before I start futzing around in there?

Thanks, in advance, for your help!

Bing

'92 Winnebago Warrior

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i would disconect the rv battery i dont know a lot on that problem but others have had to replace curcet boardsfor that.WAITER KNOWS THAT STUFF

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I've read some similar situations here in the forums, but my situation is different in that even plugged into shore power, the furnace won't ignite. The blower comes on after a few moments, but no ignition - just cold air. I've lit the stove burners and left them on, so there is LP flowing. Granted, I don't know how long it's been since the furnace was last used as the previous owners were both Floridians (as I am.) However, I travel and boondock extensively, so a heat would be fantastic.

Are there replaceable parts I should be looking at? It's a little dusty in there once the grille is off. I don't know much about coach powered stuff - should I disconnect the deep cycle battery before I start futzing around in there?

Thanks, in advance, for your help!

Bing

'92 Winnebago Warrior

All the parts are replaceable. The furnace works like this. When the thermostat calls for heat - the furnace blower comes and and blows exhaust air to the outside. There is a little switch in there that moves when the air hits it. Caled a "paddle" or "sail" switch. When it moves due to air flow -the switch turns "on" and then lets power get to the gas burner. The burner gets power and does two things. Sends spark to the electrode (like a spark plug) and turns the gas on. There is a flame sensor in there and if it sees no flame within 7 seconds it shuts down.

So, you need to check all and find out what item is not working. Sail switch, electrode (might need re-gapping), gas valve, flame sensor, etc. Sometimes the electronic control board is the problem. The most common problems are in this order - sail switch, electrode gap, and control board. Note that any obstruction in the exhaust e.g. a mouse nest or mud wasps will slow down air flow and stop the sail switch from working. Flow must be at least 75% for it to work.

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I couldn't get my furnace to light either, but when I switched to a new (full) LP gas canister it fired up. I think my sail switch needs to be serviced or replaced, but I can't find it. Does anyone know where these are located? I have a 7900 hydro flame.

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Thanks guys - I ordered a sail switch online for about $25 including shipping. Gonna take it to the trusted RV techs that fixed my water heater (bad thermocoupling.) I've learned quick to buy my own parts and was just wondering how to prioritize. I hope it's just the sail switch and maybe a good cleaning out. Thanks again!

By the way, the folks who had this Toy before me kept all the documentation - so it was easy to look up the part number from the Suburban manual, find it on eBay and order it up.

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Ive had this problem and strangely enough it lights more commonly when the engine is running. overcomes the resistance.

And yes unfortunately it doesnt light when its freezing. Tonight was the coldest night my rv has ever seen at 22 degrees and I could not get the thing lighted at all.

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Stamar, it may be your sail switch. The blower isn't running fast enough to activate the sail switch.

This may be a case where you might want to make the sail a little bit larger so it takes less air to activate it. I would not recommend bypassing it, as the switch verifiys the blower is running. The blower is needed to purge any combustible air mixture out of the furnace before doing the ignition. (else explosion can follow.

JOhn Mc

88 Dolphin 4 Auto

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My air conditioner says it's pre-wired for an electric heater element. If anyone has this how well does it work?? And does it work like the air conditioner in that the fan runs all the time whether or not the compressor is running??

On a side note the newer models of the RV propane furnace claim to be more efficient and have multiple fan speeds. Runs fast at first to warm up then slow to finish / maintain temp. Any experience with these??

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Our heater is noisy but works OK, I am considering whether or not an up-grade is worth it. When plugged in to 120 at campground we are using a small old Pelonis ceramic disk heater that is quiet and works great, we have a bunch at home.

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I get by at freezing temps with a 1kw watt electric plugged in of course, heater in much colder weather like in the upper teens the heat comes on set at 55. No way I can sleep through the blasted heater coming on. If I did more camping in the cold I would install a boat heater some thing like this, http://www.boat-heat...ine-heater.html I grew up on the Chesapeake bay and have seen these in plenty of work boats.Some of the A/C units had an option for electric heat again you'll need to be plugged in unless you can sleep through a generator.

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Mine is working today but I'm afraid to turn it off.

This is my first experience camping in the cold. I would get one of those propane can topped heaters next time

I don't think this will last long in portland but its low 20s. To ight I will run the engine and the heater and the stove to get the temperature hot then go to sleep.

The furnace is not enough to keep the rv warm even when its working. Just sort of slows down the cooling.

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And thanks waiter I will look into it I believe you are right its a sail switch and the actual fan has contracted because its frozen. Works fine at 40 degrees now. Going to leave it on.

Appreciate your advice you are the expert

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The stove is a great heater. And before you bring up carbon monoxide remember its vented with a fan.

I think its the same fan the furnace has. In a way the stove top is a better more dangerous furnace. Iit gets the rv hot enough to sweat, I think heating pans helps too.

Just an in a pinch thing not suitable for sleeping through. Actually as good or better than many peoples back up heater.

Right now its cold enough I've got everything going.

Seems like a good idea to always carry an alternative heat source so you are not reliant on a furnace that has to rely on so many items being just right for it to light.

But it is not so easy in a tiny motorhome as many of the alternatives require clearance from combustible surfaces and that is not so easy to manage. How do you stay 3 feet away from anything inside an 18' long Sunrader? Guess I will be including more non combustible surface materials when refreshing my interior. Good thing I don't mind the brushed metal look and that there are plenty of sources for stainless steel sheets and several sheet metal fabricators in my neighborhood.

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Oh duh duh its that a box was blocking the full vent not letting enough air hit the sail.

Now thhat I see how it works its obvious.

Nothing to do with cold just a coincidence.

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http://www.amazon.com/Mr-Heater-Propane-Convection-MH80CV/dp/B0000C6E2Z/ref=sr_1_8?ie=UTF8&qid=1358064880&sr=8-8&keywords=propane+top+heaterwhat about something like this?

mainea posted something similar but advertised at 6500 btu whereas this is 80000 btu

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  • 4 weeks later...

Well, it turns out that a new sail switch didn't do the trick. The techs said that power wasn't flowing from the circuit board and suggested that may be the issue. My furnace is a Suburban model DD-17DSI and the part number for the "solid state control module" is 230587. If I did my searches correctly, I've wound up looking at the Dinosaur Electronics UIB-L (Large.) http://www.dinosaurelectronics.com/UIB_L.htm

From what you all know out there - does this seem to ring true? If so, I'll order it up and see if it flies. Thanks a bunch - gotta love the internet.

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Heres a link to an older thread, there is a scanned copy of the manual there. Might be of help to you or the tech.

I didn't see a price?, Depending on the price, might consider shopping for a new furnace probably between $500 and $600.

http://toyotamotorhome.org/forums/index.php?showtopic=3640

John Mc

88 Dolphin 4 Auto

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Dinosaur boards are top notch I have used several that is a common problem on older heaters. The sail switch check is fairly simple and if it passes the problem is generally the board.

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Heres a link to an older thread, there is a scanned copy of the manual there. Might be of help to you or the tech.

I didn't see a price?, Depending on the price, might consider shopping for a new furnace probably between $500 and $600.

http://toyotamotorhome.org/forums/index.php?showtopic=3640

John Mc

88 Dolphin 4 Auto

They are running around $120 now John I think the last one I bought was 90 some thing.They are slick boards, on board diagnostics, they'll fire 3 times before they give up and the newer ones will turn the fan off if it doesn't light nice touch no cold feet standing in front of the thermostat.

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Maineah, Dinasour board may be the way to go. I like the improved intelligence of failed starts.(3 attempts then shutdown)

The old original board will just run the fan until the battery is dead. :-(

John Mc

88 Dolphin 4 Auto

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Thanks for the link, John - I do have the manual for mine (thanks to the folks who owned my 'Bago before I did. They kept *everything* that was paper.) I found what seems to be a good price here: http://www.americanrvcompany.com/Dinosaur-Electronics-UIB-L-Universal-Ignitor-Board-Large-wSpade-Connection-Camper-Trailer-RV_p_1798.html?gclid=CNz9is_gqbUCFQWCnQod1DwARg

Maineah - that's comforting news. I'll give it a go!

$77 is a fair piece better than the $192 I saw elsewhere. Especially given that I'd only really use the furnace about two or three months out of the year when I travel north out of Florida. I've posted a picture of my board below. If it looks close to any of you guys, I'll go ahead and take the leap for $77. Any more than that and I'll just invest in some flannel.

IMG_8111.JPG

Actually, just saw this:

"The UIB L works with the following manufacturer's part numbers:

Mark 10-12-2-7-7-E312, Mark 10-12-15-7-7-E002, Mark 14-12-20-7-7-E002, 05-159000-003, 05-159000-053, 05-159000-103, 05-159007-103, 05-259000-153, 1721, 3521, 230481, 230483, 230587, 315526 and 318816."

Sweet! Here's hoping it gets the job done. I'll also have them check the gap on the electrode.

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Hey, for $77, thats great. The three attempt feature is almost worth it, even if theres nothing wrong with the OEM board. I ran out of LP one night and the fan ran all night because the furnace wouldn't lite.

Keep us updated.

JOhn Mc

88 Dolphin 4 Auto

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I had one doing the same thing 90% of the time it would light but when you needed it the most that was the 10%, it was the only reason I replaced that board. I'm not sure the $77 board shuts the fan off but it does try 3 times and have diagnostics I think the fan shut off one is more expensive. So far mine have never have failed to light. Am I the only one that can't sleep thru those heaters starting? Every time mine clicks on I wake up wondering why I parked at the jet port.

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Maineah,

Thats one of the reasons I use the Mr Buddy. I'm very light sleeper, and when the Furnace kicks on, the noise makes me dream I'm sitting in the cockpit of an F-4E during engine start. :-)

One test for the new board, run the furnace, then after its lit, turn the gas off and see what it does.

JOhn Mc

88 Dolphin 4 Auto

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I think Ritabagos Dad posted it. Not sure if this is the correct one for your furnace.

Heres a link to American RV

If you get one, please post a review, At $77 this could be worth the upgrade on a working furnace.. Put the original in a box as a spare.

John Mc

88 Dolphin 4 Auto

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Check on the Dinosaur board site they have match up photos and part # so you can look for the best price on line. Fan unit --http://www.dinosaurelectronics.com/Fan_50_PIN.html

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I have a 93 winnie warrior with a suburban heater that is probably the same as yours.

You can check the sail switch by removing the cover (snaps off) and look into the furnace where the air blows out on the upper left side (as facing into the unit) - it should be up against the metal with the fan running -- I took mine & using my finger was able to exercise it.

After the fan blows for about 30 seconds then the igniter should click for a few seconds (Can see it through the window) - if it does not light this repeats 2 more times after about 30 seconds for each cycle. After that you have to turn off the thermostat to reset the process.

Note there is a gas shutoff next to the furnace - make sure it is on.

if the igniter is not clickin then most likely either the sail switch is not closing or bad igniter

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Very interesting, Looks like American RV has them for $89..

Has anyone tried this?????

John Mc

88 Dolphin 4 Auto

John, I ordered the UIB-L from American RV and my tech swapped out the boards today. Worked like a charm; she fires up and it's toasty warm in the coach. Thanks to everyone for their help in diagnosing the issue!

Ritabago's Dad

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  • 7 months later...

Correct, The sail switch detects that the blower is running to supply combustion air, and has performed a fresh air purge of the combustion chamber. This prevent the accumulation of propane or unburnt gases that could result in an explosion if they are not purged. It OK to bypass the sail switch for testing, but I would NEVER, bypass it for normal operation.

John Mc

88 Dolphin 4 Auto

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I went camping last week and it got a little cool 40's at night. My furnace usually works pretty well but my house battery was getting a bit weak. It wouldn't light so I started the engine. No joy. When I got home I plugged into shore power and it didn't light. I took my battery to get it tested as it was vintage 2006. It was bad. I replaced the battery and now it lights every time. I know my battery is getting charged when plugged in or engine running but the bad battery caused my problem. Just something to think about.

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