Anyone know anything about gas furnaces? It's cold in here! (1 Viewer)

Okay, I’m not a happy camper. A cool camper would be more like it, is in “shivering.”

Earlier this summer, a late-night thunderstorm knocked out the main circuit board for our central AC unit – cost us $350 to get it replaced. Now that we need it, we find the gas furnace is not working, and I can’t help but think it’s related, that maybe something dedicated to the furnace fried, too.

There is a small box attached to the gas valve with a four-wire plug going to it. Presumable this is what lets the gas pass through to the burners, or perhaps is related to the electronic igniter. Any way to tell of this thing is bad, or if it’s that main circuit board? What kind of voltage should I be getting on that plug to the gas valve if the circuit board is operating correctly? If I can find this out, I can probably figure out which is the problem.

By the way, I when I pulled off the cover to take a look at things, I didn’t notice any igniter glowing.

Regards,
Wayne A. Pflughaupt

You might want to post the brand and model of your system. I'm not sure what you mean by "igniter glowing"...I think most modern furnaces use spark electronic ignition with no pilot light.

My furnace (Armstrong Air model Ultra V Tech 80) had a problem too in a new home. Turns out the sheet-metal installers left a cut sliver of sheet metal in a duct and it got loose, fell down, and shorted out a switch. There are automotive-type fuses on your circuit board - check those first to ensure they are good.

IIUC the circuit board controls both A/C and heat functions. Did you check to see if you still got heat after it was replaced last summer?

Hey at least you live in TX. Mine stopped working one night when it was 15 degrees outside. I did however find out that my gas-log fireplace would keep the house from freezing all by itself.

Yeah, there’s I think a 5-amp fuse (yellow). It looks good. Didn’t occur to us to check the heat when it was 95 degrees out!

Regards,
Wayne A. Pflughaupt

When you turn up the thermostat, are you not getting anything happening? So, blower does not start up? sounds like your flame sensor is not starting, is gas getting to the burners?

Our furnace has a little window with an led, if something goes wrong it puts out a code then I can look and see what the code is and try to make a diagnosis.

Well?

OK, I'm no HVAC expert, but if this wire plug is going in the direction of your furnace and leads from the gas valve (Does the gas valve have a little dial that says something like START/ON/OFF and you use it to light the pilot light?), if so, I think that 4-wire thing is the thermocouple which controls the main gas input t o your furnace, basically, if your (gas) pilot light is not lit, do not send gas to your furnace which is a safety thing so you don't fill up your furnace room with noxious gas.... They do and can go bad and you can buy replacement thermocouplers at HVAC stores or to a lesser degree, big box hardware stores (limited). Also, the wires (copper I think) are bendable, if it's too far from the pilot light, you might not be able to start the pilot and hence, no furnace.

Also, check your main circuit breaker panel too, my gas fired boiler has a dedicated circuit for the electrics needed to my zone valves and step down transformers, etc.... make sure that isn't tripped.

Since nobody else replied, I'll add my 1 cent worth..

Jay

Glad to see you got this fixed.
I had the exact same thing happen to me, lightning storm, blown controller board, summer time, AC fixed, cold weather comes, no heat! For me it wasnt as simple as an incorrect connection. My gas controller valve was fried at the same time the controller board got fried. I had to get the gas valve fixed to get my heat going again. arrggghhh!

So since it was his screw-up, did he fix the problem gratis?

We had two new gas furnaces installed in our two-family home about four years ago and every August or September I have the service tech come out and clean and check them out. The peace of mind it gives me more than outweighs the cost. Keeps my tenant happy too. I don't care if it's 90 degrees out that day I have him crank up the heat so I know it's working.