Atwood 8535 Furance issues

[Bubbayyc]

Hello

I am new to the RV.NET world. I am having a issue with the furnace in our fifth wheel. Its a Atwood 8535-IV-DCLP. My issue is this, the furnace will run perfectly fine, but after a few days of no issues at all, it will go into the 3 tries to cycle, (fan, burner, shut down) repeat. once the 3 attempts are finish it will lock out until I reset the switch on the outside of blower housing inside the furnace. Obv a pain as we have to remove the outer cover to access the switch. What I have found through trouble shooting is that if the 30lbs propane bottle closest to the furnace is full, no issue. Once its down 20 - 30% the issues come to light. Also it simply wont run on a full bottle from the far side of the trailer.

So... it would be awesome if some of you folks had some thoughts on if this is a gas pressure issue at the furnace it self? a regulator issue where the splitter for the 2 propane bottle are? or something totally out of my current thinking?

if its the gas pressure at the furnace itself, can anyone point me to a document that shows the specifics of testing the gas pressure? I have read in a many places it need to be 11? W.C. (27mbar) just trying to verify instructions on testing a Atwood.

Thanks and sorry for the long winded post

[dougrainer]

1. You do not have to go to the furnace to reset after the 3 try lock out. Just turn the interior tstat OFF for 10 seconds. THAT will reset the Ignition module
2. You probably have 2 LP regulators if you have 2 LP tanks on opposite sides of the RV. You must have a 5th wheel?
3. IF you have 2 LP tanks NOT next to each other, the LP tank that is NOT next to the LP regulator will have a HI PRESSURE regulator in line from that tank to the other side where it connects to the Auto switchover LP regulator. That regulator drops the HI pressure down to lower pressure to prevent a HI pressure volume leak if that LP line from that side to the other side ever had a leak.
4. Yes, Lower Liquid level in a DOT tank "can" have vaporization problems when the Liquid level drops. That usually means you have excess air in tank which is hard to get that to happen, or you have moisture in the tank. Vaporization is a factor of exterior heat. The Liquid level should have no problem if you are above 50 degrees ambient. Lower Liquid level will cause vaporization problems is lower freezing type temps. If you do not swap out your tanks but refill your tanks, you may have to have them drained and purged to get rid of any air or moisture. Doug

[BFL13]

The usual pros for this topic have not shown up yet.

Meanwhile, another DIY test would be to swap pigtails on the two-way regulator, and see if all of a sudden, the farther tank works and the near one does not.

Still does not explain the failure with the half full near tank. Everything should work all at the same time with the far tank half full.

[Bubbayyc]

I came across a Atwood repair document that went into detail with respect to the BTUs of a bottle based on its percentage of fill and the outdoor temp. My other LP appliances seam to run fine, i had also read that the Atwood furnace is much more temparmental with respect to pressure than are fridges, ranges ect. However my LP gas water heater doesnt seam to have a issue. As for the splitter i am going to have a look at that this weekend, I bought a sniffer and a mamometer so i guess i will play around and see what i can figure out. Thanks for the reply

[BFL13]

You have come to the right place! 🙂

Interesting problem. The pros here will have a clue, but I'm sure it would help to report what year your RV is, whether the furnace has had any maintenance such as cleaning the orifice etc, and the make of the two- bottle regulator.

I was unaware that an LP bottle made a lower pressure than a full one. True?

If the farther bottle has lower pressure than the nearer one, does that affect any other LP appliances? Can the stove, fridge, and water heater run all at once on that farther bottle when it is half full?

The pigtails themselves can have "issues".

As a test, if the near bottle is full so the furnace works ok, when you turn on the stove, fridge, and water heater on LP at the same time, does the furnace quit?

At least you know the furnace works! That is a "good thing" ( after getting my 1991 8531 going again)