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Squid

Atwood Furnace Not Heating

20 posts in this topic

My season is getting off on a bad start. My fishhouse on wheels also serves as a bunkhouse for deer season. So, in the process of giving it a checkout Friday morning my heater didn't heat. I thought it was perhaps a bad regulator but nixed checking it out until after the weekend.

So, after checking it out yesterday I'm at a loss as to what is wrong with it. Everything seems to be working but it appears to not be getting any propane. The tank is full and I disconnected the regulator to see if gas is getting throught the valve, which it was. The thermostat turns the fan on and you can hear the ignitor but no flame. The unit is an Atwood Model 7916-II. The installation manual has a diagnostic chart but the LED indication seems to be normal (blinks on green at @ 8 sec intervals).

Has anyone else had any problems with this? I know this has been a fairly common unit to be installed in fishhouses and I'm hoping someone else out there has had a similar problem.

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Bad thermocouple or a Cobweb in the gas line of the heater.

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Do you have a gas stove top or lantern on the same line that is working? If the other things are not working, then I would say froze up regulator. If the regulator is upside down, it can let rain water get in the vent, causing it to freeze up every time it gets cold out. Been there, done that. Good luck.

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Is the battery at a full charge?

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very good point,

if you have a low battery the fan will come on

but it will not open the gas valve on the furnace.

its like below 11 volts the valve will not open,

bbqhead

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The battery was fully charged, I even swapped it with the one for the lights but it didn't change a thing. It's like the gas valve is stuck shut. I see there is a screwdriver slot on the front of the valve but I haven't touched it because I can't find any mention of it in the installation manual. Is it possible for that to get stuck? The unit worked the last time it was used at the end of the last ice season. The hose was capped at the regulator end, so I don't believe there's a blockage in the line either.

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where is this furnace located?

citywise. so many things it could be...

you can call me at 651-7175466

bbqhead

rv tech

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You may have dirt or dust on the electronic circiut board.

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The sail switch is likely dirty. It's a small safety switch located near the blower that when closed, due to the fan air flow, allows the main gas valve to open. It's a somewhat delicate mechanical switch so you could have some crud or something jamming it.

This switch is located near the blower motor. If you look on the right side of the furnace, the two wires that run along the blower duct tube go to the sail switch. Very easy to get at once the furnace is removed.

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How old is this heater? I have the same in mine. I hope its not a sign of what is to come. Please post how you fixed yours. Thanks in advance.

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I would say frozen up regulator. This happened to me a couple of years ago. Same problems. I used a blow dryer on the regulator and it solved the probelm. Water got in the little vent and froze. Just make sure the regulator is in the correct position. KOOBA

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if your getting spark and you have gas to the gas valve..id check the burner orifice. possibly clogged with spider webs,,may have to actually remove the orifice to see, depending on the type of orifice may be tough to tell otherwise

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Haven't really had a chance to look at the suggestions that everyone has come up with until today. When I tried to fire it up today I noticed that once the cover was off it would try to start up, the blower ran for a minute or two and then shut down. It was then I noticed that a red light on the circuit board blinked three times every three seconds. From the installation manual this states this is an ignition lockout fault. Any suggestions? The unit is located in Waconia.

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Squid, post your email address and I will send you a service manual. Although it could be another cause, the most likely in your case is a sail switch failure. If the switch doesn't close, the gas valve will not be energized. Could be a limit switch failure, a dirty edge connector on the circuit board, a plugged main orifice, or a couple of other things. Since you mentioned that it is the first time you attempted to fire it up this season, in all likelihood, it's a mechanical and not electrical failure. My 7920P furnace had a sail switch failure due to a mouse nest in the ducting.

Pete

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Today's the first chance that I've had some time to look into this. The sail switch seems to be working correctly. I was able to remove the blower assembly and found no obstructions to it. With a meter there was continuity with the switch closed. There was continuity across the Limit switch also. After that I swapped out the regulator with no success. The edge connector on the circuit card looked clean and all the connections looked in good conidition also. Having done all of that it's down to the circuit card, thermostat or possibly a defective gas valve. Everyting seems to be working but it just acts like the ignitor doesn't have any juice or the main valve isn't opening up. You can e-mail me at jeffmcleod2@earthlink.net. I'm at whits end on what to do next.

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Jeff, I emailed you the service manual.

What I would do next is to attempt to fire up the furnace and check for voltage at the main valve. Once the blower turns on, there is about a 15 second delay caused by the relay to purge the combustion chamber. Then, if the sail switch closed properly, you should have voltage at the main valve. If no voltage at the main valve, check for voltage at the limit switch (current runs from the sail switch, through the limit switch, and to the main valve). Easy to check and will help to isolate the issue.

Pete

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Take the spring clips that hook up to the battery off. Hook up the bazttery direct with a eyelet or a direct terminal, so that is makes good contact and give this a tryl I had the some problem and just tried mine this way and all I had to do was give the thermostat a slight tap and away the furnace went. The spring clips do not make a good connection.

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Hey folks, the problem has been solved. It was pretty much a mystery to be until I got some help and encourage from DogzLife000. When I took the burner head out there was the mystery. What should have been a empty combustion chamber had been turned into a nesting site. Over the course of the summer some unknown birds had entered through the exhaust outlet and had built one heck of a nest, complete with grass and pine needles. What a mess. The needles had dried out put some of the pitch had stayed behind. The whole furnace had to be removed and with some elbow grease, a wire brush and a vacuum cleaner it finally got cleaned out. After re-installing it there was sigh of relief when it fired up the first time and cycled just like it supposed to.

The lesson learned here for everyone of you that has this type of furnace is that when you put it away after the season make sure you block off the outlet. There will be some disappointed birds next spring but better it be them than me.

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Glad to hear it....and thanks for keeping us updated.....

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There must be a pretty good sized open outlet on it I assume.

I have my first Suburban furnace whick looks the same of a Atwood but it has a spring loaded screen cover over both vents which I assume is to prevent what happened to you.

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