Attwood Furnance

[Briarglenn]

We're old owners of a '07 3400RL Montana staying in the Seattle area and yesterday our furnace started acting up. The blower comes on and then it tries to ignite about 3 times, and then shuts down. We start the process again and then after 2-4 times of switching the thermostat on and off it will ignite.

Has anyone had a similar problem, or know of a solution? It has been extremely wet here, so I wondering if it corrosion to the electronic control board is the culprit. If so, what is the next step?

Thank you and Merry Christmas

[nailbender]

Since your Monty is almost new, I wouldn't think corrosion would be the problem. Not sure, but on most heaters the the furnace ignites before the fan starts. That allows the air to warm up before being circulated. You need to talk to Ozz, he is the HVAC expert. Hope it a minor problem.
Merry Christmas and Happy New Year

[Ozz]

It is not getting gas, or the igniter is not doing it's job. It times out after a few tries if there is no ignition.
I see it does ignite, so the spark ignition element may need adjusting, could be low gas pressure as well. Could be many things, hard to help so far away with any accuracy.
Ozz

[snfexpress]

From a previous post:

There are just a few basic parts to these blasted furnaces.

First, there is the circuit board, which is the easiest to replace. Typically, if the fan is blowing and WON'T turn off unless you either pull the 12v fuse or turn off the unit on top (there is a switch), then it is probably the circuit board.

Second, there is a sail switch. This is a switch inside the fan housing (4 screws to get the fan housing front half off). This switch has a long piece of metal on it about 1/4" wide. As the fan turns, the air pushes against this long thin metal strip and pushes it closed, which activates the switch. The switch is now allowing 12v to go thru it which in turn allows the gas valve to be able to operate.

Third is the electrode. This is a bear to replace (I did it, and it took me an hour to get the old one out and the new one in by wiggling it every which way in a very cramped space). The electrode, if bad, won't "spark" and ignite the gas. If you go to the trouble of getting the unit all the way out and on a bench, then I would take the extra time and replace the electrode.

Fourth is the gas valve. I haven't replaced this valve, and if it every gets to that point, I'm just going to order a new furnace. Looks too complicated and dangerous, at least to me.

So, in order of price, it goes 1, 4, 3, 2. Roughly $170 for the board and just a few bucks for the sail switch and electrode. Don't know the price of the gas valve.

In order of difficulty, it goes 1, 2, 3, 4.

In order of your problem, I would suggest #3. Let me ask you: Does you furnace ever light? The unit will try 3 times, then "lock out", so you have to turn the unit switch off then back on. When you turn it back on (with the t-stat turned to furnace and calling for heat - set to 99 degrees), the fan should come on, then the ignitor on the circuit board (after about 20 seconds) should go click, click, click and then the propane should be burning. If the propane does not ignite, the exhaust sound will not change, and then the board will try a second and a third time.

Oh, I would try one thing first. Open your stove hood and disconnect the gas to the burners. Fit a gas guage on to the propane supply line. It should read between 10 and 14 inches WC or about 3 lbs of pressure. But, Atwood's manual states that before doing a pressure check, to first disconnect the propane supply and cap this supply line to the furnace. If the pressure is low, go to your regulator and adjust as necessary (under the black cap on the regulator).

Sorry for the long post, and hope that what I wrote makes sense to you. Good Luck!

[Illini Trekker]

I don't know how long the heater has been running properly, or if you have recently changed a bottle. I once change a bottle and there was a bend in the hose that slowed the flow enough to have the same results your having.

[EagleRunner]

You might be getting air in the system. Check the hose connection to the bottles to make sure they are tight. Some of these bottles are very finicky about how tight that connection is. If both tanks are full, try switching the cross-over valve to the other tank and see if the problem persists.

Good luck!

[richfaa]

Furnace lights, then fan comes on,comes up to temp, furnace turns off, Fan continues to fun for awhile... that is normal. There have been a few times, after a period of non use..when the furnace will start, stop a couple of times then run normal. Don't forget there is a time delay in the operation..I think it is 45 seconds so if it starts and stops it will not start again for 45 seconds.you have got to wait it out.