How Do I Turn My Heater Fan Off?
Dec 27th, 2008 by Kirsten
Posting from: Philipsburg, MT
Listening to: Eastmountainsouth, Winter
I just want to turn my damned heater off. The fan runs nearly constantly. It does shut off occasionally, but by what algorithm it chooses to do so I have no knowledge. Here’s all I have in this rental house as a temperature control:
At my house in Arizona, I have a switch that lets me choose Cool, Heat, Fan Only or Off altogether. When I use the heater in Arizona, if the temperature drops below my setting, the heater kicks on. If it is above my setting, the heater turns off. That is what I want here. I would be happy if it is warmer than 65 in here, if I’m getting that for free such as via the sun through my south windows.
However, my heater doesn’t seem to allow that. With the exception of the mysterious random shutoffs, if the house temperature is below my setting of 65, it blows hot air. If the house temperature is above 65 IT BLOWS COLD AIR. >:-( It is about 25 F outside right now. If I get too hot inside WHICH I WON’T!, I could just open the window for five minutes. Instead, I am sitting here at my dining room table with the fan blowing cold air on me unless I turn up the heat so it will blow hot air on me. This is a huge waste of energy and money. I just want to turn it off. Does anyone know what it would take for me to do this? I am in a rental house and don’t want to replace the thermostat if I don’t have to, but I am now seriously considering this.
Here’s what it looks like inside. Does this tell me anything useful?
The glass capsule is a mercury switch. But I do not think the thermostat is the problem. From what you describe it sounds like the fan itself is somehow disconnected from the switch. So it always stays on. The heating system shuts off, but the fan does not, therefore you get cold air.
My guess is that it should be easy to fix, but you need access to the heating system itself.
Good luck.
PS. You need a “preview comment” option.
Is it running constantly, or near constantly?
Have you tried banging on it……………seriously sometimes they get sticky and like a dog, kid, or wife need a little lovin’.
Today it has been running constantly. However, I do know that some days it does turn off. What should I be banging? Is it a good idea to bang equipment involving a glass capsule which contains mercury?
Put the cover on it and just think Lil’ K told you that “your sister is better doggie than you”
You’re drinking Long Island Iced Teas again, aren’t you?
Hey Kirsten:
A gas furnace first ignites the gas and spends some time heating the elements. Then when the elements become very hot, the fan is engaged. When the house reaches temp the gas is shut off, and the fan stays on to extract the last heat from the elements. Your thermostat is a bi-metal spring that uses the different temp-co of the two metals to set the angle of the mercury switch with engages and dis-engages the heater. You should be able to get a nifty digital one at a home center for about $40. I can program a week long temp profile that has 4 time zones for each day.
How does this mercury switch work? When the mercury is touching the leads on the inside of the capsule on the right side, are the heater and fan supposed to be on? If so, does that mean if the mercury is not touching them, the fan should go off shortly thereafter?
The fan should shut off once the furnace has cooled down “enough”.
Two possible problems. One is that the airflow in the furnace is reduced due to a clogged filter, in which case changing the filter will solve the problem (the furnace isn’t cooling down fast enough, so the fan runs too long, and also the heat part of the furnace doesn’t run long enough because it gets hot too fast). That’s the easy fix, and in winter you should probably be checking the filter every month. In places with forced-air heat, I tend to buy furnace filters in boxes of a dozen so I always have spares on hand (and they’re a lot cheaper by the dozen).
Second possible problem is a sensor in the furnace. For that, I get an HVAC repairman out with his tools and bits to just check everything over.
Hey Kirsten:
I can’t say I know the default switching logic of heaters. But that mercury rocker switch is just making and breaking connections. It depends on the logic of the relay. It can be normally open, or normally closed. Normally meaning what is the condition of the relay when the coil is not energized. Also it can be a latching, momentary, and toggling relay. Oy gavelt! My bet is your rocker switch is providing and cutting power a a coil on a switch relay that is driving one or more other relays. What’s it doing, only FSM, the Engineer and a HVAC person may know. My gas heater has like 3 relays on it and when I get back to town, I have to replace one as well as replace the pilot light nozzle. DaveP’s observations sound very germane too.
Hey Dave P:
I was having the same problem with my furnace as Kirsten. Your solution sounded to be right on and as proven to be the answer. “Not enough air flow to cool down the furnace quickly”.
I wanted to thank you for the solution.
I should see if it’s the solution to my problem as well today. We took the filter out completely yesterday right before I left for Helena, and then I got stuck here overnight due to a blizzard. I should be back in Pburg with a new filter later today.
K, Even if you can’t find a new filter, just pulling out the old one (it’s okay to run without it for a day or two) will let you know if that’s the problem. Quick and easy diagnostic test. Good luck!
Glad to help, John.
It would if I was home.
I pulled it out and then left and haven’t been home since. Even if it didn’t solve the problem, it definitely needed a new filter.
I am bummed. I do not think this fixed my problem. At least this tidbit helped someone out. Good work on that, Dave.
However, I have been home for a while now and the fan has not been off at all. I haven’t even put the new filter in yet. Sometimes it blows hot, sometimes it blows cold, but so far it has not gone off at all.
I don’t think the fan is disconnected from the switch because (a) it has been off in the past, and (b) p says he thinks it went off while I was gone. If it was disconnected, I would think this would be a hard failure instead of an intermittent.
I looked in the Do It Yourself book p’s family gave me for my birthday and it’s no help on this particular topic either.
I am now reading through this.
An intermittent failure on the fan like that is probably one of the temperature sensors within the furnace. Like a false “on” from the one that says “hey, things are hot enough for you to blow now”. But that’s the point where each furnace’s design varies enough that I back off and leave further diagnosis to the pros, partly because they have service manuals and such, and partly because they have access to the replacement parts.
But that thread sounds like good advice, and gives more detail on the “stuck sensor” problem I figured was possibility 2.
I don’t suppose you’ve typed the name of the furnace manufacturer into Google along with words such as “fan won’t stop”?
Several years ago I came across a similar problem at a client’s house. The solution in that case was to follow the ground and ensure that it is properly affixed..
That said.. since this is a rental, how about a call to the landlord? This is really a problem that he/she should resolve..
Victory! Kel fixed the heater today, and I think I know how to do it again if the problem recurs. It seems as though the limit switch had just gotten dirtied up enough that it wasn’t functioning so the fan always stayed on because nothing was telling it that the furnace had cooled down enough. We think this has been a problem before because Kel found a box down by the heater with two more of the same switch in it that had previously been used. Anyway, I know how to take the switch out, how to clean it off and how to replace it now. As long as I don’t have to ever install a new one, I should be good to do this on my own from now on.
Yes, this is technically a problem that the landlord/landlady should take care of. However, back when I moved into the house in April, my stove had one non-functioning burner that they kept promising to fix. It was not until a second burner went out that they finally replaced the stove about seven months later. And then I had to get prometheus to help me carry the old stove outside, bring the new stove inside and then wire the plug onto it. If I have to wait seven months for this to get done, it would be July before my heater was fixed. These folks are nice people, but they aren’t very good about maintaining this house as far as what the owners should be responsible for. It’s not their electric bill, so they don’t have a great incentive to take care of it.
Glad to hear you guys solved the problem!
These folks are nice people, but they aren’t very good about maintaining this house as far as what the owners should be responsible for. It’s not their electric bill, so they don’t have a great incentive to take care of it.
This sounds very much like our landlords. They very uncharacteristically did a lot of work on our house late this summer, including replacing a patio door … but all the door trim (interior and exterior) is still outside, getting rained and snowed upon, waiting for them to return and reinstall it. By the time they get to it, the stuff will probably have several inches of moss growing on it.