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Old 11-24-2021, 06:32 AM   #1
Twinlakes
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Gas furnace

We have a 2021 3231CK and the gas furnace is not kicking on. We are full timing in Colorado at 9,000'. Need help quick! thanks


Update, after a series of off/on cycles, it finally kicked on.
 
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Old 11-24-2021, 07:35 AM   #2
ChuckS
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Most likely if it had not been used in a while or the LP tanks were changed the furnace LP line still had air in it..

Normal sequence of events will always be.
1. Blower motor turns on and purges for 45 seconds
2. Sail switch moves to complete circuit via airflow from blower
3. Igniter fires and LP valve on furnace opens
4. Light off occurs.. furnace runs till set point reached
5. LP valve closes, furnace flame off, blower motor runs for 30 seconds to cool the furnace combustion section

IF light off doesn't occur the sequence of ignition retries 3 times and if not flame detected then it goes into lockout mode

To clear lockout mode turn furnace OFF and back ON.. sequence above will start again

Another weak area is the (Black ATC) style looking fuse often used on the Dometic/Atwood furnace.. This is not a standard fuse.. it is a resettable fuse that often doesn't function correctly and can give problems
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Old 11-24-2021, 08:35 AM   #3
jsb5717
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If the furnace is attempting to ignite, meaning you can hear the igniter clicking, then the sail switch is working correctly. If your furnace isn't trying to ignite then there are are a couple possible causes:

Sail Switch - this is the easiest thing to check first. It's easy for a bit of lint to get sucked into that switch, preventing it from closing and allowing ignition. After a few attempts it is possible for it to clear. But it's 2 screws and 2 wired connectors to remove and check it. Make sure it's clean. Since it currently sounds like an intermittent issue I would suspect the Sail Switch.

If the Sail Switch is clean then it could also be your control board
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Old 11-24-2021, 10:07 AM   #4
R.S.O'Donnell
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Quote:
Originally Posted by Twinlakes View Post
We have a 2021 3231CK and the gas furnace is not kicking on. We are full timing in Colorado at 9,000'. Need help quick! thanks


Update, after a series of off/on cycles, it finally kicked on.
Ours was doin the same. It was acting like the flame sensor/ignitor wasn't detecting a flame until it had gone through several tries. I attempted to remove the ignitor but too much had to be removed to get it out with the time I had so I put the screws back in. Inexplicably it worked flawlessly after that. It's been working perfectly ever since.

This is the best explanation I've found on how they work:

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Old 11-24-2021, 11:01 AM   #5
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Originally Posted by R.S.O'Donnell View Post
Ours was doin the same. It was acting like the flame sensor/ignitor wasn't detecting a flame until it had gone through several tries. I attempted to remove the ignitor but too much had to be removed to get it out with the time I had so I put the screws back in. Inexplicably it worked flawlessly after that. It's been working perfectly ever since.

This is the best explanation I've found on how they work:

Interesting, but is that an RV furnace? Looks residential to me. Unless there is a recent change the igniter would be the spark type that you can hear clicking as it attempts to light. That same scenario, though, was happening to us. ie.: actually igniting but turning right back off. For us it turned out to be the propane regulator, which wasn't supplying a flow adequate for the high demand of an RV furnace. New regulator solved the problem.

Question for the OP is whether the furnace is failing before or after the igniter attempts to fire. That will help to trouble shoot if the issue is pre or post ignition.
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Old 11-27-2021, 09:27 AM   #6
R.S.O'Donnell
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It is a residential but from what I understand the flame sensor functioning is similar. In my case it must have been some glitch with the flame sensor (which is integral with the spark ignitor).

Quote:
Dometic™ Atwood 35100 Hydroflame RV Furnace Igniter Electrode
The furnace electrode is both a conductor establishing an electrical spark at the Burner to ignite the air to gas mixture, and a sensor to signal the circuit board the flame is established.

Mine would light for a few second and the gas valve would abruptly cut off. After repeating this several times on it's own it would relight and stay lit.
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Old 11-27-2021, 12:27 PM   #7
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Originally Posted by R.S.O'Donnell View Post
Mine would light for a few second and the gas valve would abruptly cut off. After repeating this several times on it's own it would relight and stay lit.
Yeah, that's exactly what ours was doing. At first it would eventually stay lit after several failed attempts and resets. Ultimately it was still the regulator. The OEM regulators on these aren't great. A new Marshall Excelsior solved it for us.
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Old 12-01-2021, 02:35 PM   #8
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If someone has not already noted, the circuit board on the furnace has a flashing error code light. 1 flash every 3 seconds for example means "airflow not proven" (i.e. sail switch problem). Other codes for other issues. Check dometic furnace manual.
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Old 12-01-2021, 03:00 PM   #9
Bob and Jeannette
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Quote:
Originally Posted by jsb5717 View Post
If the furnace is attempting to ignite, meaning you can hear the igniter clicking, then the sail switch is working correctly. If your furnace isn't trying to ignite then there are are a couple possible causes:

Sail Switch - this is the easiest thing to check first. It's easy for a bit of lint to get sucked into that switch, preventing it from closing and allowing ignition. After a few attempts it is possible for it to clear. But it's 2 screws and 2 wired connectors to remove and check it. Make sure it's clean. Since it currently sounds like an intermittent issue I would suspect the Sail Switch.

If the Sail Switch is clean then it could also be your control board
At the rally a Dometic Tech told me that the previous generation of sail switch (last year included) had a design issue and was prone to fail. I had replaced mine last winter and Amazon sent me another old design. Works so far.
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Old 10-16-2022, 08:06 AM   #10
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Hi Chuck, been reading all replies about furnace issues but did not see mine. Furnace works for awhile, then in middle of night stops. I turn off and then turn in again, blower runs but no clicking or ignition attempt. I turn off and on a few times with same result. However on two occasions I went outside, removed cover, turn that little switch that says OFF and RESET to the Off position. I wait few minutes and then put it back to RESET position, then the thing works! Any idea on that?
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Old 10-16-2022, 08:13 AM   #11
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Originally Posted by Bkuhn View Post
Hi Chuck, been reading all replies about furnace issues but did not see mine. Furnace works for awhile, then in middle of night stops. I turn off and then turn in again, blower runs but no clicking or ignition attempt. I turn off and on a few times with same result. However on two occasions I went outside, removed cover, turn that little switch that says OFF and RESET to the Off position. I wait few minutes and then put it back to RESET position, then the thing works! Any idea on that?
Yup.. its a cheaply made switch and I would simply order me a knew one and replace it and that should cure your issue with that.. Personally its a dumb switch... Its located on the top of the case and is called a maintenance switch..

those that have the Atwood furnace that has no front access panel have to remove a bsasement rear wall, etc to gain access to that switch...
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