# Furnace Won't Light



## russk42 (Sep 10, 2007)

I've checked some of the previous posts on the topic, and there seems to be plenty of expertise out there, but I need a little more help in troubleshooting: 
Thermostat activates the furnace blower(s?), they run for a few minutes, but no ignition. While the blowers are running I hear a noise which may be the gas valve going on and off? this noise repeats a few times over the course of 30 sec. or so; but it doesn't have a pitch or frequency comparable to the ignitor for the fridge, so I'm guessing that it's not the ignitor. if I stand outside the exhaust, I smell a little gas, and there appears to be plenty of air flow. My guess is that my igniter is fouled or otherwise hosed up. But before i tear the whole thing apart, i thought i'd see if anyone else has any suggestions.

so...As I wrote above, I'm guessing that the noise I hear while the furnace is trying to light (less than a half dozen knocks over 30-60 sec.) is a gas valve, not the ignitor---what does the furnace ignitor sound like? It's always worked flawlessly before, so I've never noticed.

I've tried purging the gas lines by lighting the stove, and I've also tried a different --and full-- LP tank, (the one from my gas grill--it should have sufficient pressure, no?)

should i go ahead and pull the whole thing out? I can't see any obvious way to access the combustion chamber. I'd like to get it open without disconnecting the gas, is that possible?

thanks in advance


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## H2oSprayer (Aug 5, 2006)

have you tried looking here?


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## Oregon_Camper (Sep 13, 2004)

Running on electric or battery?

Double check the battery connections are clean and tight. If you don't have the proper power running to the heater, the circuit board will detect this and not allow the system to start.

I had the same problem and for $120 the Mobile RV Tech was able to find my problem...yep, a loose terminal. Ouch...Live and Learn I guess.


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## russk42 (Sep 10, 2007)

thanks for the replies...
I've been on shore power, I might have to check the connections---I saw your earlier posts Oregon--- but first: can anyone tell me what the furnace igniter should sound like? is it a clicking like the fridge? (Im NOT hearing a rapid clicking) I'm just wondering, because everything else seems to be happening (i.e. blower, gas, cycle time) I won't be looking into it again until Saturday, so I'm trying to gather information first. i don't want to start ripping things apart until Im sure of all my symptoms


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## webeopelas (Mar 11, 2006)

Even on shore power, if your battery is low or failing it can cause the furnace not to start, because it runs on DC power. Had that happen at the Grand Canyon. On shore power, but the convertor failed and was not charging the battery. Got real cold when the furnace wouldn't light.

So as said before, check those connections and check the charge in your battery if you can.


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## D1Boz (Oct 18, 2007)

You will hear a clicking and it trying to start. Ours will go through that cycle like 3 times and shut off and I will have to reset it like 3 times before it will keep lit. One time though it wouldn't lite after trying over and over and took it to the dealer and they replaced the thermostat I believe but it would still take like 3 tries even after that. I just chalk it up to not being used a lot and the gas trying to get to it.







Good Luck!!!!


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## California Jim (Dec 11, 2003)

Yes, you should hear a loud, rapid & distinct TICK-TICK-TICK-TICK-TICK-TICK-TICK as the igniter fires attemting to light the burner.


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## KMinton (Mar 7, 2007)

When I had this problem it turned out that a small amount of trash was in my regulator. That reduced the pressure just enough so the furnace would not light but everything else worked fine. I changed the regulator and have not had a problem since. It appears that the furnaces are very sensitive when it comes to the operating pressure.

Kelvin


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## russk42 (Sep 10, 2007)

I pulled the furnace, checked it on the bench: sail switch OK, limit switch OK, gas valve OK...but no spark. Looks like I'm due for a new control board at $100+...or I may just use a pair of $10 portable electric heaters this spring. here in VA, this time of year, we only need heat at night...especially if we cook inside.


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## Chasn'Racin (Mar 12, 2007)

If you are on shore power and you can find them, we use the old style "oil filled" heaters. They work great, heat the space well and are very safe. Plus the cat love's it BOL


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## Oregon_Camper (Sep 13, 2004)

russk42 said:


> I pulled the furnace, checked it on the bench: sail switch OK, limit switch OK, gas valve OK...but no spark. Looks like I'm due for a new control board at $100+...or I may just use a pair of $10 portable electric heaters this spring. here in VA, this time of year, we only need heat at night...especially if we cook inside.


Guess its time to have someone actually repair the furnace...sorry.









Guessing you don't dry camp a lot, as you speak about the electric heaters.


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## Cabana Dave (Jan 29, 2007)

Hi RUSSK42,
How did you make out with the furnace? Mine fires up, but does not stay lit. I would remove the furnace, but it seems a little to involved for my skill set. Did you find it easy to remove? All I was able to test was the overheat switch located in the very front of the heat exchanger.

Thanks,
Dave


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## russk42 (Sep 10, 2007)

Cabana Dave said:


> Hi RUSSK42,
> How did you make out with the furnace? Mine fires up, but does not stay lit. I would remove the furnace, but it seems a little to involved for my skill set. Did you find it easy to remove? All I was able to test was the overheat switch located in the very front of the heat exchanger.
> 
> Thanks,
> Dave


Not too hard to remove... the hardest part was getting a wrench on the gas line. 
In my 28rss, the furnace is under the dinette, behind a drawer. i took the entire drawer frame out (5 or 6 screws)
2 or 3 screws holding the unit on the floor.
4 wires with wire nuts to disconnect---don't forget to label.
Wiggle the unit to pull the exhaust and intakes free.
Good luck


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## Cabana Dave (Jan 29, 2007)

Thanks I'll give it another try this summer when we don't need it. I hope yours is working now.

Dave


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## snowtakampers (Apr 29, 2006)

I had a similar problem. Had the furnace running fine. I turned it off and came back later and it wouldn't start. I could hear it trying to start, I even could smell the propane coming out of the vent. Convinced it was an electronic problem I took it to a dealer to have it repaired under warranty. It turned out that the repair was not covered. Apparently hundreds of lady bugs had crawled in through the vent and clogged the burner. The fix was a $5 screen that fits over the vent. the problem was that there was $200 labor. A very expensive lesson. If you don't have one I recommend the screen that attach to the exterior heater vent with springs


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## Cabana Dave (Jan 29, 2007)

I hope you all weren't holding your breath for this response, but I finally got around to the furnace repair. Last week we went down the shore with the 21RS. DW and I walked to the campground RV store/repair center, and inquired what it would cost to have a tech come to the sight to look at the furnace. $105 for a 1 hour site visit. The repair would be more. This was motivation to break out the tools (whatever was in the back of the Yukon), and pull that baby out myself, and bring it up to them. I removed 3 screws, the gas line, and 4 wires like RUSSK said. I photographed the wire connections with my digital camera before removing. Then with a generous amount of force she came out. I dropped it off at the service center, and they had it ready by the end of the day. It turned out to be the circuit board (of course). The next day it took me an hour or so to reinstall and test it. Here's the total $$$: new Suburban board $129, labor $35, 4 wire nuts $1. Oh well, we now have a working furnace, and we were still able to get to the beach that day.


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## russk42 (Sep 10, 2007)

Cabana Dave said:


> I hope you all weren't holding your breath for this response, but I finally got around to the furnace repair. Last week we went down the shore with the 21RS. DW and I walked to the campground RV store/repair center, and inquired what it would cost to have a tech come to the sight to look at the furnace. $105 for a 1 hour site visit. The repair would be more. This was motivation to break out the tools (whatever was in the back of the Yukon), and pull that baby out myself, and bring it up to them. I removed 3 screws, the gas line, and 4 wires like RUSSK said. I photographed the wire connections with my digital camera before removing. Then with a generous amount of force she came out. I dropped it off at the service center, and they had it ready by the end of the day. It turned out to be the circuit board (of course). The next day it took me an hour or so to reinstall and test it. Here's the total $$$: new Suburban board $129, labor $35, 4 wire nuts $1. Oh well, we now have a working furnace, and we were still able to get to the beach that day.


Glad you got it fixed...we found that the small electrical heaters were preferable, since they're much quieter. I'm still procrastinating on the furnace, but the whole issue makes me wonder what makes the circuit board die in the first place? I've seen replacement circuits online for $89---I wish I could know if they're reliable.


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## Cabana Dave (Jan 29, 2007)

russk42 said:


> I hope you all weren't holding your breath for this response, but I finally got around to the furnace repair. Last week we went down the shore with the 21RS. DW and I walked to the campground RV store/repair center, and inquired what it would cost to have a tech come to the sight to look at the furnace. $105 for a 1 hour site visit. The repair would be more. This was motivation to break out the tools (whatever was in the back of the Yukon), and pull that baby out myself, and bring it up to them. I removed 3 screws, the gas line, and 4 wires like RUSSK said. I photographed the wire connections with my digital camera before removing. Then with a generous amount of force she came out. I dropped it off at the service center, and they had it ready by the end of the day. It turned out to be the circuit board (of course). The next day it took me an hour or so to reinstall and test it. Here's the total $$$: new Suburban board $129, labor $35, 4 wire nuts $1. Oh well, we now have a working furnace, and we were still able to get to the beach that day.


Glad you got it fixed...we found that the small electrical heaters were preferable, since they're much quieter. I'm still procrastinating on the furnace, but the whole issue makes me wonder what makes the circuit board die in the first place? I've seen replacement circuits online for $89---I wish I could know if they're reliable.
[/quote]

We actually use one small electric when it's needed. I just hate when something is broken. The service tech told me the after market boards have a 3 year warantee, but don't fit.









Happy heating! Dave


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