Furnace and thermostat

Most furnaces have a high limit safety switch that shuts The burner off if the temperature inside the furnace gets too high. That might be your problem. The temperature inside the furnace can get too high if the blower Is not moving enough air because of a clogged filter Or a number of other reasons. Is this a gas or oil furnace? M

I have a Lennox MERIT® SERIES Model G40UH-36A-070X 03 gas furnace.

The filter is clean.

I can see two green LED lights (Diag#1 and Diag#2) through a "port-hole" on the front of the furnace.

Above the "porthole" is a "SureLight Diagnostic Code/Status of Furnace" cha rt.

When the fan is running and the burners are lit, the LEDs have a simultaneo us fast flash (which means "Normal Operation").

But, when the fan is NOT running and the burners are NOT lit, the LEDs have an alternating slow flash which means:

a. Burner failed to ignite b. Limit open more than 3 minutes c. Lost flame sense 5 times in 1 heat cycle d. Pressure switch opened 5 times in one heat cycle.

Here we go again. A few days ago you had a similar thread where you had all kinds of issues with a Totaline thermostat not being able to raise the temp over 76 when set to 82. So, now you come in here and start a whole new thread, as if starting from fresh, with a different thermostat, not mentioning the previous history?

If two thermostats didn't work and you are having the above problems, I think it's time for a service call. Also, I suggested in the other thread that you connect the two wires for heat together and see if the furnace would run continuously. Had you done that, you'd have known it wasn't the thermostat long ago. Or maybe you're just trolling.

It might be the flame sensor. It might be possible to fix it by cleaning it, or it might need replacement. A service tech can probably figure it out right away. That's what fixed it when I was having what sounds like a similar problem.

Bill

Yes. My question would be:

Was the furnace not working with the old thermostat? Replacing it, to solve the problem was the wrong choice...the problem is with the furnace.

OTOH: If the furnace was working fine with the old thermostat, then is it wired wrong? two wire vs three wire for example

You really need a good pro to help you. We've told you what to do a few times. In particular I told you to get one of the round Honeywell or similar thermostats. It could also be the furnace does not have the power to raise the temperature as high as desired.

I cleaned the "flame sense" rod and it resolved my furnace problem. Now our furnace is again working correctly (i.e., the room temp is now above freezing!).

The price of a pad of steel wool was much cheaper than calling in a HVAC technician who would try to sell me a new furnace for a gazillion bucks.

condo owner posted for all of us...

This is a repeat post from the poster whom didn't pay attention the first time.

trader_4 posted for all of us...

Oren posted for all of us...

He should snuff out any flame or sparks he sees because everyone knows gaz blows up!

My first post was about a Totaline thermostat. This post is about a Honeywell thermostat.

Two different subjects = two different posts.

OK. From now on, I will add all NEW topics to my ORIGINAL post.

But that means that thread will contain many disjointed topics.

The thing is there was just one overall problem, that you could not get the heat in the house over 76. So, starting a new thread about your new thermostat that you bought as part of trying to solve that, without the context of what went before, just wastes a lot of time for anyone who hasn't followed the other threads, doesn't realize you're the same poster, etc. Additionally, if you had followed some of the simple advice given in the first thread, ie just connect the two heat wires and see if the furnace runs continuously, you'd have avoided a lot more screwing around, purchase of a new thermostat, etc. Some people we just can't help from themselves.