Furnace Issues

[dandr614]

I have recently tried to fire my furnace to no avail. Full propane tanks, hot water heater working, burners on stove top working.

Furnace fan turns on, hear clicking outside, but no ignition. Went through the cycle several times and actually got flame at one point as could feel hot exhaust air on outside of 5th wheel. Last few times did not get ignition.

Don't suspect air lock/purging issues but just not sure what could be causing this. Have read a lot about sail switch issues but fan would not run if that was the case, correct? Could it be an obstructed flame tube?

Thanks in advance.

[fonzie]

Are you on shore power or only on battery? If battery is low then the furnace blower might not blow enough to activate sail switch.....

[dandr614]

hooked on shore power.

[Flybob]

There is a safety that will shut off propane after several failed attempts. it is possible that is is tripped. Shut off furnace ( not just lower thermostat) to reset the safety, then try again. You may need to pull fuse for furnace depending on your thermostat.

[Dinostop]

A couple years ago I found that the air intake for my furnace had spider webs in it and would not allow enough air flow which prohibited a flow switch from activating which would not allow the furnace from starting. I blew compressed air in and resolved it.

[dandr614]

Thanks Flybob. I have been turning the furnace off and back on and it will go through the sequence again, no different results.

Dinostop I will check and see if I have any obstructions. Thanks for the replies.

[dandr614]

Latest update,

No restrictions that can be observed. Have removed front cover. Gone to electric heaters as I am on shore power, guess I will need to get someone to come out and take a look at it.

[YoungKopernik]

It sounds to me like a thermocouple issue but it could be the board too.
If your furnace goes through its purge cycle, then you hear the spark click and you can feel heat for a few seconds in the outside exhaust. I would guess the thermocouple is not seeing the flame.
Now for a story: Camping in the cold rain and our furnace went out on the 5th day so I pull out the multi-meter and start checking everything. It did the same as yours; it would go through the cycle and start for a few sec then go out. I almost had the furnace out when I went out side to pull the exhaust and FOUND IT. My wife had left a umbrella drying on a table blocking the exhausted, the umbrella was all burned up. It sure made me laugh
Campers are Fun
John

[MNtraveler]

Originally Posted by YoungKopernik

It sounds to me like a thermocouple issue but it could be the board too.
If your furnace goes through its purge cycle, then you hear the spark click and you can feel heat for a few seconds in the outside exhaust. I would guess the thermocouple is not seeing the flame.
Now for a story: Camping in the cold rain and our furnace went out on the 5th day so I pull out the multi-meter and start checking everything. It did the same as yours; it would go through the cycle and start for a few sec then go out. I almost had the furnace out when I went out side to pull the exhaust and FOUND IT. My wife had left a umbrella drying on a table blocking the exhausted, the umbrella was all burned up. It sure made me laugh
Campers are Fun
John

OMG if you can laugh about that, you are a good humored person! 😨😀

[dandr614]

Is there a generic part number for this suburban thermocouple?

[KyDan]

Please post the make and model # of your furnace.
It very likely does NOT have a thermocouple.
It probably has a flame sensor which is not the same.
Modern LP furnaces and water heaters and even LP refrigerators have
flame sensing technology which does not use a thermocouple.

IF it's lighting only sporadically and then not staying lit once it does light the
control board is suspect. You can try polishing the spark electrode with
extra fine sandpaper and make sure any push on connectors going to/from
the board are tight (pull them off and replace them a few times to help make
sure they are not corroded at the plug).

Dinosaur boards are highly regarded as better than new and usually a bit
cheaper than original. I had to put one in my last rig after my furnace exhibited
pretty much the same symptoms you say you are having.

[YoungKopernik]

Yep going to need a model# and then a wire diagram and/or schematic.
I never leave home with out them, for each major appliance. I hope not to need them but they sure are a life saver when you do need them.
Doing some thinking and it could be a bad or sticky solenoid too.
Its hard to diagnose stuff from a distance but its just a puzzle one piece at a time tell one is missing/bad.
Good Luck
John

[northstar1960]

Originally Posted by dandr614

Is there a generic part number for this suburban thermocouple?

x2 on the flame sensor . but do not polish, a very slight cleaning will do . one does not want to take sand paper to it and polish it so much as a very lite and simple clean a couple stroke will do . the sensors will get carboned up and not sense flame and causes what you are experiencing

[dandr614]

Thanks all I will pull the control board as soon as I return. Luckily it has not gotten real cold yet and my ceramic heater seems to be working well enough for the time being.