Intermittent Atwood Furnace Malfunction

[BayouBiker]

You can make a cheap flow tester with some paper and scotch tape. a paper cylinder to fit snugly around the black plastic duct register cover the end with a half moon paper and the other half use tape as a hinge and another oversized half moon as a flap. then check each register to see if the flap opens about the same amount.

[GCinSC2]

Originally Posted by BayouBiker

You can make a cheap flow tester with some paper and scotch tape. a paper cylinder to fit snugly around the black plastic duct register cover the end with a half moon paper and the other half use tape as a hinge and another oversized half moon as a flap. then check each register to see if the flap opens about the same amount.

Brian, good one nice and simple.

Each model, different routing and flow. A good visual insp and look for maybe something that fell from storage onto hose or restrictions to return air flow. My furnace is under the sink and pulling the shelf allows for a good peak at the hoses. Then follow to distribution registers.

In one of Darren's videos the bench test one IIRC he said do not put any type of filter in the return air flow.

Sitting here waiting for the rains to hit from Sally a bit latter.

Gary

[moby_1851]

Quick update: first much thanks to all of you! First - thus problem has been intermittent since May. I went months without and issue and a few weeks ago it recurred. At the end it went from an occasional non response to the thermostat to no ignition at all. Three tries and ignition lock out fault. So after replacing the sails switch 3x, replacing the limit switch 1x I zero'd in on the spark electrode. Replaced it yesterday (a little challenging but doable by an idiot like me)....butkus. Blower on/gas on/click on the electrode...no flame....lock out. My next move was to replace the board with a Dinosaur universal. Did this yesterday and the furnace fired right up...Cycled all evening with no problems. I need a couple of weeks of normal ops before I fully trust it - but good sign. I assume my board was slowly failing - and seemed to not work at all at the end. Interestingly my Atwood was modified prior to my purchase - Atwood had a defect where the horizontal boards were being damaged by water - compartment leaks and pools on the board. So their fix was to pitch the board up at a 45 degree angle. the Dinosaur won't fit the bracket....so I used a little velcro tape to gently fit the board in - velcro rather than a screw now holds the bracket. The board isn't secured to anything but the velcro'd bracket keeps if from pitching up and the cushion of wires keeps it from dropping....so its not tight but not going anywhere. All I could think of

[Shads Shack]

A quick check would be the ground wire connection in the external compartment.


Corrosion can shut the entire system down, and can be intermittent.


I now check the connection periodically as it has shut me down a couple of times.

[Big Thunder]

Originally Posted by moby_1851

I have a 2018 International with an Atwood. my problem is intermittent - sometimes weeks go by, sometimes hours between issues. Naturally it doesn't happen when I have a tech on scene - so everyone is guessing.

First - the furnace works. The blower and flame are fine. When I set the thermostat the furnace blower goes on and the flame ignites.

The problem is after - as noted - a week or a day - of normal operations, the furnace will suddenly not respond to my temperature setting on the thermostat.

The first time the temp dropped into the 40s inside - I woke up cold and that was the start of it.

To get the furnace to restart I turn the thermostat off and on again and it starts.

I have replaced: 1) The wall thermostat 2) The limit switch 3) The sail switch AND sail switch bracket. I am on my third sail switch in 23 months so I feel safe saying it isn't any of these issues. Somebody suggested a blockage in the ducting, but except for the bathroom (which is small - so I assume its not the issue), I get good air our of all. Any ideas?

We had the same problem and discovered it was the sail blade. It MUST be able to move freely, also, it's position in relation to the switch is very important!