Furnace continuously cycling

Larcifer · 01-11-2021, 04:41 PM

2020 High Country

Furnace continuously cycles every 1:15 min. :15 sec blower cycle(normal) then fires for 1:00 min. I get 3 blinks on the control board light. Unfortunately RV is skirted so I can't take it in and so far the mobile techs I've contracted are all in the South.

Suggestions?

ChuckS · 01-11-2021, 04:50 PM

Since you have an LED on the igniter board the furnace is a Dometic/Atwood series...

3 blinks indicates the board is going into lockout mode because flame sensor is not seeing the flame... is the furnace actually lighting off and producing heat?

**sourdough** · 01-11-2021, 04:54 PM

I had the exact same problem with an Atwood 35k furnace and it was the control board replaced under warranty but Chuck has given you another angle to look at - or have looked at.

Larcifer · 01-11-2021, 05:18 PM

Quote:

Originally Posted by ChuckS

Since you have an LED on the igniter board the furnace is a Dometic/Atwood series...

3 blinks indicates the board is going into lockout mode because flame sensor is not seeing the flame... is the furnace actually lighting off and producing heat?

Yes, it produces heat for 1:00 min then shuts down for :45 sec while it goes the restart cycle(3 blinking lights) then :15 sec purge cycle before the 1:00 heating cycle.

Is there a way to test the board? If I replace it is there an upgrade. Also not impressed with the cheap Dometic thermostats. Upgrades?

Thanks!

**chuckster57** · 01-11-2021, 05:27 PM

If the board is replaced under warranty, your required to use the OEM board for reimbursement. If your not worried about getting paid back then get a dinosaur brand board.

Larcifer · 01-11-2021, 05:38 PM

Yeah it's no longer under warranty. I'll go with the Dinosaur if I need to replace. I'm going to test a couple more things first and go from there.

Thanks for the help!

**chuckster57** · 01-11-2021, 05:41 PM

There is a way to test the board but the test equipment to do it isn’t cheap.

ChuckS · 01-12-2021, 12:52 PM

Since the furnace is actually firing up and producing heat then shutting down you might want to take a good look for something obstructing the intake and exhaust..

I’d also take a good look at the hi limit switch on that furnace. It should read continuity all the time... if furnace is actually overtempimg then it might make sense why your seeing 3 flashes on the LED.. it’s locked out from igniting to prevent further overtemp...

At least I believe that’s how the igniter module board should respond...

Also a loose connection on the hi limit switch or back to control module could be suspect

You could TEMP connect the two leads going to hi limit switch and run furnace to see if short cycle still occurs... if not then either you have a bad hi limit switch or an air flow obstruction

And I cannot stress the word TEMP enough ... it’s to Test ONLY

Larcifer · 01-14-2021, 05:11 PM

Well after three days of trouble shooting the starting and and stopping of my Atwood furnace. Initially it would work for about 15min. At the end it would intermittently work for about :45 seconds. I finally tracked it down to a power issue with the help via phone of a local RV tech that winters in the south.

The power issue turned out to be a faulty 15amp fuse🤦🏼*♂️. I wasn't sure whether to laugh or beat my fingers with a hammer.

I now know more about an Atwood furnace than I ever care to know! Not to mention the valuable lesson of learning that cheap fuses can actually be faulty.

Furnace works great. Now just hoping my RV doesn't blow away in the 60+mph winds we are experiencing in the Black Hills.

Thanks for all the support and suggestions!

**chuckster57** · 01-14-2021, 05:15 PM

Glad to hear you got it. As long as the stab jacks are down you should be good. We spent the night In Wyoming in 2009 with 70mph winds, the trailer “ wiggled” but stayed in one piece.

Larcifer · 01-18-2021, 08:06 AM

Good to know!

Cascadia · 01-24-2021, 08:14 AM

Quote:

Originally Posted by sourdough

I had the exact same problem with an Atwood 35k furnace and it was the control board replaced under warranty but Chuck has given you another angle to look at - or have looked at.

We just dealt with the same thing with ours! You would think a furnace would last longer than a year! We were lucky to find a tech nearby since the dealer didn't have any mobile techs due to covid. We have an extended warranty so it cost us $100 and is guaranteed for 5 years. He said the new furnaces are junk...I have to agree!

jkatona22 · 01-24-2021, 08:21 AM

Quote:

Originally Posted by Larcifer

Well after three days of trouble shooting the starting and and stopping of my Atwood furnace. Initially it would work for about 15min. At the end it would intermittently work for about :45 seconds. I finally tracked it down to a power issue with the help via phone of a local RV tech that winters in the south.

The power issue turned out to be a faulty 15amp fuse🤦🏼*♂️. I wasn't sure whether to laugh or beat my fingers with a hammer.

I now know more about an Atwood furnace than I ever care to know! Not to mention the valuable lesson of learning that cheap fuses can actually be faulty.

Furnace works great. Now just hoping my RV doesn't blow away in the 60+mph winds we are experiencing in the Black Hills.

Thanks for all the support and suggestions!

I have a 2020 H/C Montana, I have the exact same issues, which 15amp was it. This furnace is driving me out of my mind.

jkatona22 · 01-24-2021, 08:32 AM

I forgot to ask could you send a picture of the fuse box and port out what fuse it is? my trailer is skirted also , and there isn't a mobile repairman in area of Michigan i am in.

mike and peggy · 01-24-2021, 09:27 AM

Hi. I've had similar problems with 3 of the RVs we've owned. In all 3 cases, I found that the black wire that comes from the control board and goes into the heater was touching against the outside metal door to the heater compartment. What turned me on to this solution was when I would open the door to look at the heater, the heater would start properly and stay on. When I would then shut the door and go back inside the RV, it would act up again. I then realized that the black wire (I assume it is a temp sensor wire) would touch the door when it was closed and somehow interrupt the signal or the temp it was reporting. I just put a slight bend in the wire so it wouldn't touch to door anymore and no more heater problems (until we got a different RV).

This may not solve everyone's heater problem but making sure that the wire is not touching anything else (ie the metal door) before it gets to the control board is worth a try.

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