furnace diagnostics

[L0veless]

we are in AZ no need for furnace other than to knock off the early morning chill.
furnace has been working like charm except today.
furnace blower turns on then ignites for 5 second then off with blower still running tries to ignite again does ignite then 5 seconds turns off while blower still running.
this is what I have done so far to try and diagnose the issue.
propane tanks were filled couple days ago had no issues yesterday.
I turned all three burners on high on cooktop when turned furnace on no drop in flame output.
all fuses are good
circuit board led lights up once at beginning of cycle then off again just one blink.
reading posts most common issue seems to be the sail switch how do you test this?
second common thing is the circuit board again how do you test this.

I have no issue replacing both parts but would like to know which one went bad. rather then replacing them and still having this issue.

oh yes furnace compartment has been/and is dry, no cobwebs very clean compartment.

thank you

[DQDick]

Have you tried switching the reset switch off and on?

[Carl n Susan]

A good place to start is here in the Files section. There is a "RV Furnace Troubleshooting" manual that will guide you through the diagnosis.
*Clicky*

[L0veless]

yes I did multiple times, any other ideas?

thank you

[bigred715]

I have the same problem down here in Arizona. Furnace hasn't worked since early February. Replaced the switch over regulator and the red 30 PSI regulator. When the furnace tries to light the green indicator turns to red. Had tanks topped off, to no avail. The sail switch is located inside fan housing according to drawings so can't take out and check. Little red led blinks once. Tried lighting furnace once again recently and furnace ran longer, 10 seconds and shut down again. Don't know what to do.

[L0veless]

well the heater is now working as it should.
I took the circuit board to a dealer they tested for free it was ok.
sail switch also tested out ok.
limit switch was the issue replaced and no issues now.
for those having the same issues as I did here was the sequence as explained to me
first blower comes on to clean out the chamber if the sail switch is bad then it shuts down.
then ignition if no ignition then its a bad igniter, if you have ignition then shuts down after 5-10 seconds the limit switch is bad.
to test gas pressure turn on all stove burners and then the heater if there is no deviation in the stove then you should have enough pressure for the heater.
now that I have learned about this unit it is really pretty simple.
hope this helps some one down the road.

[L0veless]

also if your unit cycles 3 times with running properly it will go into lockdown mode then you have to turn it off and remove the fuse wait couple minutes to reset then replace fuse and turn back on.

[bigred715]

Well, I got home from Arizona on April 3 and decided to test furnace before putting trailer in storage and guess what...... the furnace came on and it worked. Ran for about 5 minutes and decided it was OK. Go figure.

[Rsmarlow82]

If not already fine, remove burner assembly, and make sure it is clean, and dry Burner holes might be partially plugged.. we found water in ours������

[Weeda]

I had the same issue. I switched the reset button on and off, worked for about an hour. Reopened the furnace door and pushed all the connections into their counter part and I've had no problems since. Hope this helps

[lj_cox]

Originally Posted by Rsmarlow82

If not already fine, remove burner assembly, and make sure it is clean, and dry Burner holes might be partially plugged.. we found water in ours������

This was our issue, after multiple misdiagnoses from service techs, we took the igniter assembly apart. The igniter was sparking fine. The burner assembly and orifice were totally rust-clogged. I ordered new parts, and on a whim tossed the burner into a 24 hour vinegar soak, which did a super job on the rust. Cleaned up and reassembled and it's been working like a champ ever since. Kinda peeved about the $$ spent on failed "fixes", especially since the manual recommends regular cleaning.

[Rsmarlow82]

Sad part for us was it happened first time we tried to lite the furnace on a " brand new unit" Glad yours is now ok