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Old 10-11-2011, 11:51 AM   #1
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Atwood Furnace won't start

Hi everyone hope someone can help. I have a 2000 Coachman Class A with an Atwood furnace that won't fire up. when I turn up the thermostat the fan comes on then shortly I can hear some clicking at the valves, but no ignition. It then shuts down and there is a red light on the board that flashes three times steadily. There is a tag that says this means ignition lockout? Any idea's what I need to do?

Thanks, Sam

Model 8940-lll-DCLP
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Old 10-11-2011, 12:10 PM   #2
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Sounds like air is still in lines. Try again several times. If it dont lite, maybe regulator?
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Old 10-11-2011, 12:41 PM   #3
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Turn the LP on? Its trying to lite the fire, but cant. First thing to check is LP getting to the furnace..
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Old 10-11-2011, 01:00 PM   #4
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Quote:
Originally Posted by drolds442w30 View Post
Hi everyone hope someone can help. I have a 2000 Coachman Class A with an Atwood furnace that won't fire up. when I turn up the thermostat the fan comes on then shortly I can hear some clicking at the valves, but no ignition. It then shuts down and there is a red light on the board that flashes three times steadily. There is a tag that says this means ignition lockout? Any idea's what I need to do?

Thanks, Sam

Model 8940-lll-DCLP
Hi , and welcome to iRV2, as other posters have stated it sounds like there is no (or poor) propane supply at the furnace. Are the other propane appliances working ok ? The main valve at the propane tank is equiped with a ruptured line shut off, in the tank. If the tank valve is opened rapidly when the lines are empty the valve will cut propane flow by 95%. To re-set the valve , close the tank valve and open very slowly , allowing back pressure to build in the lines; all appliances off; then light the stove top burners to check for full flow from the tank. Then try to re-start the furnace.Hope this works for you.
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Old 10-11-2011, 02:13 PM   #5
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Let's see......

Lack of propane
Bad sail switch (that I NEVER found on mine)
Clooged heat exhanger (mud daubers nest, etc)
Electric ignition sparkers not correct distance apart
Blown out burner (my favorite)

Check for propane at furnace. You should be able to smell it when it tries to start.

Do you have a can of compressed air? Use it to blow any and all dust off of the control board at the furnace.

Air compressor? Blow air through where the ignitor/burner is and feel for air at the exhaust. Look in exhaust with a flashlight (take the extension off) and look for nests.

Check the distance betwen the sparkers.

Remove exhaust extension. Disconnect propane at the valves. Disconnect wires. Remove 5 (I think) screws and pull the valves/burner out. See what it looks like.

One of my burners had a hole blown in it about the size of a quarter. Heat and use took it's toll. Replaced at it runs like new.

Good Luck!
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Old 10-11-2011, 02:15 PM   #6
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Quote:
Bad sail switch (that I NEVER found on mine)
Clooged heat exhanger (mud daubers nest, etc)
......
Blown out burner (my favorite)
The ignitor is 'igniting' therefor the sail switch is working eliminating a bad/clogged burner...
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Old 10-12-2011, 07:07 AM   #7
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Thanks for all the replies, I have a 1/2 tank of propane all other appliances including the refrigerator are working fine on gas. No nests etc. Blew it out with compressed air. Air flow thru it when started is very good and I can smell a whiff of gas after a click. So I'm thinking an igniter problem. But the red light on the board is still blinking 3 steady blinks??? And the tag says this is an ignition lockout?????

Thanks for all the help.

Sam
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Old 10-12-2011, 07:59 AM   #8
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Copied from another forum.......................

IYou should have a sticker on your blower assembly giving you the fault codes, but I'll post them here for you.

Fault LED Indication

Internal Circuit Board fault Steady on, no flashing

Limit switch/Airflow problems 1 flash with 3-second pause

Flame Sense fault 2 flashes with 3-second pause

Ignition Lockout Fault 3 flashes with 3-second pause


So it appears you have an ignition lockout fault.
That would mean that the electronics is not detecting a flame that MAY be there.
Maybe a bad ground at the electronic board.
Or, the sparking you hear may not be taking place at the place it should be.
Possibly a bad spark electrode or high tension wire.

A "flame sense fault" would mean that the board sensed the flame at trial for
ignition, but then lost the flame signal.

This electronic board senses the flame thru flame rectification.
Basically, a flame will pass a DC electrical current. In this case thru the spark electrode to ground (the burner).
So your "spark wire / electrode" is also part of your flame sensing circuit.

To reset your board all you need to do is:
1. Turn your t-stat on off switch off.
2. Turn down the temperature so the bimetal points will open.
And wait for the fan to shut off, if it hasn't already.

To restart, flip the switch back on and turn up the t-stat.

You can go to the Atwood site at : Heating Systems - Atwood Mobile/ There is some information here and a trouble shooting guide.

BUT remember you are working with LP gas, be very careful. If you are the least bit unsure of what you are doing,
please take it to a dealer. It's better to pay a few bucks and be uninjured and still go camping."

Maybe this will help!
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Old 10-12-2011, 08:13 AM   #9
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FWIW, generally if there's a flame, even just a temporary flame, you'll hear it roaring easily. No roar=no flame.

Personally, I would restart the cycle several times (turning the t-stat off, then back on) before abandoning hope. If the furnace hasn't been used in a while that may be necessary. If that doesn't do it, it's time to start serious troubleshooting.

Regarding troubleshooting, if you get a whiff of raw propane, it sounds to me like you might have an ignitor problem. I would look to see if something hasn't fallen on to the electrodes, shorting them out?
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Old 10-12-2011, 04:22 PM   #10
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When mine did this, it was a bad electronic control board.
Replaced the Chinese made board, and all is OK now.
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Old 10-12-2011, 06:57 PM   #11
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Both of my furnaces have had similar probs, but more precisely, they would momentarily light off and then shut down, which led me to flame sensors. For 4 bucks each, I haven't had an issue since last March.
Jim
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Old 11-02-2011, 04:55 PM   #12
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JCBOUNDER where did you get your flame sensors? My Atwood 8535-III is doing almost the same thing. On mine however, the fan stays on after trying to light. I can hear the burner fire up but, then it just goes out.
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Old 11-02-2011, 08:05 PM   #13
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Mine is doing much the same thing.. It starts normally, It ignights well, I can hear the flame and feel the heat.. Then it shuts down.. normally after about 3 seconds of flame.

I'm in communications with Attwood..... believe it or not they are answering my E-mails.
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Old 11-02-2011, 09:53 PM   #14
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Different wiring setups for different furnaces which is why the fan in one will keep running and not in another.
Ignitor board will initially detect a flame sense error however, because of the 3 try lockout feature, it will end up with lockout error after 3 tries. You have to watch the LED through the cycles.
No flame sense can either be bad ignitor, bad high tension cable, corroded high tension lead connectors or defective ignitor board. When mine acted up, the lands on the ignitor board were failing due to flexing due to repeated heating/cooling over the years. Replaced it with a dinosaur board which also has the fan shut off feature at lockout. A little rewiring to add that option but not difficult.

As I posted on Wa8yxm thread, Ignitors are available at Marksrv.com Hydroflame - Atwood rv furnace parts. posted manual and P/N information with it.

The 8535-III (Coburncliff) information is contained in the general Atwood service manual at http://bryantrv.com/docs2/docs/hflamefurn04.pdf. There are 2 wiring diagrams and you will have to determine which model you have. The one at the bottom of page 10 called 85-III Local sense, is a 1 wire ignitor. The high tension lead is used for spark voltage and flame sense. The one at the top of page 11 called 85-III remote sense has a 2 wire ignitor. High tension lead for spark and a seperate monitor lead (black wire).
For all cases, ignitor, and sensor for 2 wire, cleanliness, condition, and adjustment are important.

Wa8yxm's fan will shut OFF at lockout because the fan is controlled by the ignitor board. Coburncliff will not shut fan off because it is controlled by the Thermostat via the Time delay relay.

Like a pilot light gas valave, there is only a small millivolt signal back to the ignitor board for sense.

Dave
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