problems with 8531 Atwood IV

[goducksgo]

I am having problems with 8531 Atwood IV.Blower comes on then it ignites and heat comes out of the exhaust.Burner then goes off and blower continues.It then ignites again etc.3 times then locks out.I swapped CB with other furnace and no change.I adjusted electrode no change.Burner has rust on screen,is this OK?Cleaned wire connections with eraser.Used dielectric grease.No change!! What to do next??
Voltage 13.6 gas pressure? But other furnance works fine

[RV Wizard]

Pests could have obstructed either the air flow or the LP gas flow inside the unit. If so removal and cleaning may be required to remove the obstruction and check the ignitor/flame sensor for proper gap and operation.

[goducksgo]

I had a mouse in the area.I had burner out,I gapped it to 1/8,tip was maybe 1/4 inch from screen.Is that OK? The burner chamber is around the corner?So air flow restriction would be in heat chamber where ducts flow into coach?Sounds like I need to take whole unit out to get to distrbution box where ducts start? Thanx

[Dave78Chief]

Control board is not sensing that the burner is lit within 10 seconds so it shuts the gas off. Blower continues to run as part of the cool down/purge evolution. Keeps retrying to light the unit until lock out. The electrode has to be in the flame path as it sends a monitor signal back to the control board. Make sure the connections and lead from the electrode to the control board are clean and tight. There is only a millivolt monitor signal being fed back to the control board. If all that is good, then the control board is bad.

Troubleshooting the RV Furnace

http://www.atwoodmobile.com/manuals/...0SP%201.08.pdf

Dave

[Gary RVRoamer]

As Dave says, the furnace control board is shutting it down after ignition. The only reason it ever does that is if no flame is sensed, so it has to be either the igniter/sensor or the wiring from it to the control board. Last resort would be a bad board simply not recognizing the sensor signal, but that is rather rare.

[RV Wizard]

Quote:

Originally Posted by goducksgo I had a mouse in the area.I had burner out,I gapped it to 1/8,tip was maybe 1/4 inch from screen.Is that OK? The burner chamber is around the corner?So air flow restriction would be in heat chamber where ducts flow into coach?Sounds like I need to take whole unit out to get to distrbution box where ducts start? Thanx

Gap should be 3/16" between electrode and ground probe or burner. Clean any rust off burner for electrode spark path. Clean electrode of any carbon. make sure there are not mud dobber nest in the combustion chamber or heat exchanger (inside or out). Good luck and keep us posted.