Atwood 8535-IV Furnace - Short Cycling?

[Newbe2020]

This thread is old but hoping to help someone like me who just ran into a problem with a new-to-me-motorhome searching for answers.
My class A atwood furnace would fire up, run 3-5 minutes and shutdown the burner (fan would still blow hot and gradually get colder as heat is removed from the furnace) and then fire the burner back up after a new cycle.
After replacing the thermostat and propane 2 stage valve without change, I decided to look into the airflow issue someone here mentioned before attempting to get at the high temp limit switch.
My RV had 3 four inch ducts and 1 smaller 2 inch duct leading to the bathroom. As indicated on someone's previous post, this is not enough ducting for the furnace as it trips the high limit temp switch.
After removing the small duct from the furnace leaving a gaping hole for plenty of hot air to escape it NO LONGER SHORT CYCLED.
I am adding a 5th 4 inch duct to the furnace that will direct heat toward the cab as there currently isnt a duct going to. Hopefully this will solve my problem. I will try to update this once complete.

[Waiter21]

Newbe202, Welcome to the Forum.

I had similar problem. On mine, the round vent louvers could easily be closed and block off airflow. I( I think they would sometimes close by themselves). I physically removed the "adjustment" portion of the louvers so they are 100% open, all the time.. No more short cycling.

I want to look into adding another vent just to help it some more..

[Newbe2020]

[QUOTE=Newbe2020;5144092]This thread is old but hoping to help someone like me who just ran into a problem with a new-to-me-motorhome searching for answers.
My class A atwood furnace would fire up, run 3-5 minutes and shutdown the burner (fan would still blow hot and gradually get colder as heat is removed from the furnace) and then fire the burner back up after a new cycle.
After replacing the thermostat and propane 2 stage valve without change, I decided to look into the airflow issue someone here mentioned before attempting to get at the high temp limit switch.
My RV had 3 four inch ducts and 1 smaller 2 inch duct leading to the bathroom. As indicated on someone's previous post, this is not enough ducting for the furnace as it trips the high limit temp switch.
After removing the small duct from the furnace leaving a gaping hole for plenty of hot air to escape it NO LONGER SHORT CYCLED.
I am adding a 5th 4 inch duct to the furnace that will direct heat toward the cab as there currently isnt a duct going to. Hopefully this will solve my problem. I will try to update this once complete.

UPDATE: FIXED
Furnace heats the rv up to set temp of 72 without shutting off at all until it reaches the right interior temp.
I Installed a 5th duct running towards the front of the motorhome placing the vent on the wall near the door to direct more heat up in the cab area.
I am really confused as to how this passed through QC at the manufacturer. Way to go Jayco

[TRIPLE 555]

Originally Posted by Newbe2020

This thread is old but hoping to help someone like me who just ran into a problem with a new-to-me-motorhome searching for answers.
My class A atwood furnace would fire up, run 3-5 minutes and shutdown the burner (fan would still blow hot and gradually get colder as heat is removed from the furnace) and then fire the burner back up after a new cycle.
After replacing the thermostat and propane 2 stage valve without change, I decided to look into the airflow issue someone here mentioned before attempting to get at the high temp limit switch.
My RV had 3 four inch ducts and 1 smaller 2 inch duct leading to the bathroom. As indicated on someone's previous post, this is not enough ducting for the furnace as it trips the high limit temp switch.
After removing the small duct from the furnace leaving a gaping hole for plenty of hot air to escape it NO LONGER SHORT CYCLED.
I am adding a 5th 4 inch duct to the furnace that will direct heat toward the cab as there currently isnt a duct going to. Hopefully this will solve my problem. I will try to update this once complete.

After replacing the Atwood 8535 for a new Dometic (Dometic bought them out) and connecting the mystery hose ,the heat has surely gotten better.Coulda,shoulda,woulda took pictures of all the huge knock-outs for ducting available on top and sides of both new and old furnace.
With the Poweblanket Extreme heating the sub zero propane tanks to Florida like temperatures you might cook an egg on the metal registers closest to the furnace.
Might have to add 5th hose as you say so overlimit switch won’t cut out.

Going more propane and not so much electrical at 0.19/kwh ,with tax in ,sure doesn’t hurt my feelings.

Super short burner on/off cycling can be caused by these new fangled valve, catastrophic spring loaded safety yo-yo device.If a higher than normal propane flow is detected ,it reverts to a yo-yo valve that just blows/burns and repeats.
I usually have turned valve to propane on very quickly ,so have to shut off both tanks ,unscrew both fittings,retighten,,and reset by SUPER-SLOW opening of the valves.