My digital thermostat displays current temp, temp at which to turn on heat, and when the heater is running, it says heater on... except now it's also saying that the heater is on when it isn't, and since it thinks it's already on, it doesn't actually come on, no matter how cold the house gets. If I manually move the turn-on temp below the actual temp, and then back up, it stops saying that it's on, and then it does come on.

I don't know if the problem is with the heater, or the thermostat, or both, but I sure hope someone does, because once I've gone to bed, and so can't keep adjusting the temp, the heater won't come on any more!

 

Welcome to the forums.

It sounds like your furnace is going into a fault mode.
When the fault occurs several times the furnace can go into lockout.
Lockout can be reset by turning the power off to the furnace or turning the thermostat down and back up.

You're going to need furnace servicing.

 

How does one turn the power off to a heater? There's no obvious way to do it. And if I can do that, it will fix it, but it will still need servicing?

 

Your heating plant should have a switch either on it or nearby that you turn off to service the appliance. Some people have an additional switch at the top of the stairs. There may be a red plate on the switch.


Turning the power off is the same thing as turning the thermostat down and back up.
You are resetting the fault but not fixing anything.
If you don't have a service company.... call your gas provider. They usually have good techs.

 

There's no obvious switch; it's in a cabinet-type enclosure, so the switch might be where it can't be seen, on the sides or back? Where is it usually located on a unit?

 

If it's in a closet it can be just outside the closet. There is no set location.
It's there to turn the power off to service the unit.
If you don't readily see it you may not have one.

 

No, there's no switch outside the closet... but there HAS to be a way to turn it off, right, since every unit has a way to be serviced? If there's no switch, what am I looking for?

 

Maybe it plugs into the wall ?
If not then it's going to be controlled by a circuit breaker.

When you open the blower door... there should be a safety switch that will shut the unit down.

 

No, there's nothing plugged into the wall, and when the unit was serviced a few years ago, he didn't touch the circuit breakers, which are in my bedroom closet... so I'm looking for a safety switch to turn it off? What does the blower look like?

 

You could post some pictures for me...... How to insert pictures.
If it's a standard furnace... the blower is behind the bottom service door.

 

I'll try to get someone to take pics for me... meantime, you know that I also don't know where or what the bottom service door is, right, lol? The safety switch is behind a door that's behind another door?

 

If you are still having problems with the furnace faulting.... you're going to need someone to service it.
Finding a power switch isn't going to solve the problem.

With most furnace there are two service doors. They usually lift up and off.
The top larger door is the burner door.
The lower smaller door ls the blower door.

 

This has been FIXED, and with something so easy it can barely be called a repair... by my husband, NOT a repair person! It did NOT need servicing! And it was FREE, no new parts required!

The heater issue got steadily worse; it eventually became clear that no heat was coming out of the vents part of the time, which had gone unnoticed with the coldness in the house from the heat not coming on at all. This allowed my husband to find the solution on another site:

To find the reason for the lack of heat, he had to open the heater cabinet, turn off the lights, put on the heater, watch for the flames to come on, and then count how long they stayed on before going out. If it was just a couple of seconds, different repair, but if it was 8+ seconds, easy fix... and that's what it was!

There's a little metal sensor that looks like an allen wrench, whose job is to make sure that there's flame when there's gas coming out. If it doesn't heat up enough, it turns the gas off as a safety measure... but, if there IS flame, what it actually does is turn it off and prevent heat from being generated.

What happens is, over time this little thing can get coated with carbon; it wasn't much, it looked like almost nothing, but it's a good enough insulator to cause increasingly frequent failures. The solution; scrub it with steel wool! 5 seconds of effort, stick it back in, and PRESTO, perfectly functioning heater!

Oh, and this model, an old Rheem, doesn't have a cutoff switch like pictured above; instead, when you take off the panel, there's a thing that pops out, that gets pushed back in when the panel is replace. Kind of cool.

 

Your furnace was not installed to code. Code has always required a disconnect/service switch.
I discussed the door safety switch back in post 8.

You still have a gas fires furnace that requires routine service,
Furnaces are not install and forget appliances.

 

I don't believe for a second that the power company guy who checked the heater wouldn't mention a glaring code violation like that. Not everyone can know about every kind of heater; my husband found someone who DID know what to do, so all is well.