Atwood heater shuts down after 6 mins

[Arnold88]

Hello . tried the search button before i made this post

so I recently purchased a 2016 Keystone vapor lite 28v toy hauler.
it has an atwood AFMD35121_A furnace
currently have it plugged in to my house in a 110 outlet

I am having an issue with the heat in it . if you turn the heat on it will run for roughly 6 mins then shut down.
did some diagnosing and when it shuts down i loose power to tstat tested it it does not have 12v .furnace fuse is still good and has its 12v. let unit cool for 10-15 mins flip reset switch on top of unit and it will run again for another 6 ish mins then trips reset again tried this 4 times. same out come every time. something is getting hot and tripping the reset dont know what .

At this point im leaning to the control board . im thinking it fails when it gets hot. it seems like its a pretty common item that fails.
any help would be greatly appreciated.

Also there was a number listed on the control board on a sticker it says zhongding 30575 A 2215 16018 is this the pn for the board?

there was also another pn that is on a sticker that was under the control board that has a pn of 37821 C

this is my first rv so this is all new to me

[bobbecky]

There should be a 12 volt breaker wired to the furnace power source that may be opening up. If so, when it cools, it would close and you would have power restored. Maybe that breaker is the problem. Have you verified that your gas supply is adequate, not lowering pressure to the furnace? This is a link to the Atwood Service manual of your vintage furnace. https://www.google.com/url?sa=t&sour...wNSO8XvWkCT2Ru

[Arnold88]

thank you.
i will look into the propane. l will look for the circuit breaker tomorrow and see if i can warm it with a heat gun and see if it fails

[JRTJH]

Originally Posted by Arnold88

thank you.
i will look into the propane. l will look for the circuit breaker tomorrow and see if i can warm it with a heat gun and see if it fails

There was a "recent" (about 18 months ago) service repair to remove all the 15 amp 12VDC circuit breakers from the furnace wiring system and replace with a 15 amp "blue" fuse... The reason given was that the circuit breakers "weaken over time" and start to open at lower and lower amperage draw.

All of the 12VDC circuit breakers I've seen are in the furnace slot in the 12 volt power distribution panel.

Another issue you may have, since there seems to be a 6 minute delay from furnace ignition until shutdown, is a blocked warm air ducting issue. There may be pet hair, dust or something else either caught in the squirrel cage fan blower or even a rat's nest or some other restriction in one of the heat duct runs. As the furnace operates, if there is not enough air movement through the heat exchanger, the temps will rise and the "HI LIMIT" safety switch will open to shut down the furnace.

I'd check for any circuit breaker in the main DC fuse panel and then start checking for a possible air restriction in the ducting/air movement system in the trailer.

[Arnold88]

I removed the unit last night one of the panels was off the side of the unit it looks like at one point it was taped back on but fell off. So it was wide open blowing hot air into that small tight spaces where they stuffed the furnace .
I’m going to clean out the area today where the furnace sits re install and test . I didn’t notice anything inside the squirrel cage but I will look a little closer at it tonight .

There are blue 15a fuses in my circuit panel . The furnace fuse is a blue 15a I removed it before I pulled the unit . So I don’t have a circuit breaker in there . Thank you

[Arnold88]

Yup was definitely a temp issue the knock out panel that fell off and was just blowing heat straight into the area where the heater assy was placed was the issue I screwed it into the box taped everything up and put the furnace back in place and it ran till it satisfied temp

[mrs.aron.mack]

Thanks for posting this. We just bought a used 2018 Keystone passport 2520 RLWE and it has an Atwood AFMD30121 – A furnace. We took it out for the first time over Easter and also noticed the six minute cycle. The blower stays on for 18-25 minutes, but the burner is only lit for 6 minutes or so at a time. (I grabbed the stop watch). We took it to the dealer and they can’t seem to resolve the issue. I was starting to think maybe we were stuck with a battery killer of a furnace.

I am going to share this link with the service tech.

[mrs.aron.mack]

Just found this on an Atwood Forum. Depending on the serial # of your furnace there is a recall on the furnace limit switch.

https://myrvworks.com/wp-content/upl...mit-Switch.pdf

[Arnold88]

Thanks I’ll look into that .