When the ignition is on the furnace fan runs, I took It in for service, they said Its low in LP, I wasn't going for it, But they filled the tank and It worked great, Well the tank is empty now. And the fan is on again, I have the gas valves off and the thermostat off. It has good air intake. When you turn the thermostat up the fan speeds up. So what?, could it be a fan relay, or sensor?
This Argosy came to me one dark rainy night, and that was the start of the remodel, and every one on this site has been a great encouragement, thank you all! sandra
I assume you have a Suburban NT30 or something similar. If not, disreguard the following.
The furnace is designed so that the fan comes up to speed before anything else happens. If it fails to ignite for any reason (and an absence of LP would certainly be a reason) the fan will continue to run indefinitely. Of course, turning it off at the thermostat should shut it down IF you actually turn it off. Simply turning down the thermostat will not shut it off.
If you have, in fact, turned off the furnace at the thermostat, and the fan still runs, I am at a loss. Could be a bad limit switch, of course. Could be a bad thermostat. The latter could be checked by the simple expedient of unscrewing the red lead(s) at the back of the themostat.
Not to excuse my poor diagnostic skills, but some more details would be helpful - kind of thermostat. Exact model of furnace. A more complete discription of the problem.
Usually, you will get a bunch of sometimes different answers.
I agree with Mark, first disconnect the thermostat and check if the fan is running.
If it is........
On units as old as ours (antique, vintage, just plain old), it is possible that many modifications may have been made by the Previous Owners (PO's), and not only do you have to trouble shoot the actual problem, but also problems that may have been caused by the POs.
The fan running when the ignition is on is a real puzzler. One possible explanation is that the PO had a "thing" (light, clock, fan, whatever) that he wanted "hot" all of the time, and this "thing" was already connected to a wire controlled by the ignition switch.
It is possible that the PO tapped into the line going to the fan, and electricity is now backfeeding from the ignition controlled "hot" back to the fan, causing some decreased voltage to run the fan.
Not saying that this is the cause, only a possibility.
My unit has been a never-ending source of joy and frustration this past year as I have tracked down ghost voltages, internal wire separations, corrosion, extra wires, and other unexplained phenomena in the quest to make a 20 year old moveable reliable and livable.
One of the things we share here on the Forum is the quest to keep these aging American Icons useable and affordable.
If you don't have a good voltmeter, get one. If you don't know how to use it, take a course at an evening college in automobile repair for dummies, and prepare to get to know the innards of your Argosy intimately and on a first name basis.
Keep us posted on your successes and failures - we learn from each other!
Good Luck!
__________________
Dennis
"Suck it up, spend the bucks, do it right the first time."
the drone and I removed the furnace and bench tested it and found the fan switch was not working, so off to the shop, they tested and replaced the fan switch. tested again and found every thing was working but would only run for about 2-3 minutes. that left only the circuit board. it was replaced, and we are now set to go. thank you all for your input
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