Furnace problem

[chris_swany]

When I just recently turned on my furnace for the first time since last winter it is not working properly. It seems to turn on and I can watch and the pilot light lights properly but nothing happens after that. The pilot light seems like it is lit to a proper height. I turned the fan onto on ratehr then auto and that blows air fine. So I am not sure what is wrong and any help would be appreciated.

Thanks

Chris

[NotNorm]

I'm in the same boat. It got a little cool last night and I decided to start up the furnace. Everything seems fine, but it doesn't kick off on it's own. The furnace itself is about 50 years old, but I managed to wire it to a digital timed thermostat about three years ago. The thermostat seems to be working just fine. If I push the temperature setting up past the current ambient temperature, I hear a switch in the thermostat click. Usually I would also hear a matching click in the furnace as well and then the "whoosh" of the burner starting up. But that's what I'm not hearing this year. If I go down to the furnace, there is a button that I can depress and hold for 30 seconds which will start the furnace up. I did this last night and it did kick off to the point where the blower started when it's startup temperature was reached, but once the shutoff temperature was reached, the system was off again and didn't turn back on. Last year I had to have the thermocouple replaced, but that doesn't seem to be the problem this year. Anyone have any clues? I admit I am a total "newbie".

[NotNorm]

Chris,

Just a thought, but have you tried manually shorting the wires at your thermostat to see if your heater starts up? I'm not sure what kind of thermostat you have or how many wires, so I can't tell you wich ones. But if your thermostat has labeled terminals, you will probably be looking for a ground and a heat on. One other caveat, I WOULDN'T short the wires on a thermostat that uses 110 VAC. Mine uses 18 VAC, so it's a possibility. And of course if you're not confortable with electricity, then you should have someone else test it.

Notnorm

[NotNorm]

My problem is solved! It appears that I had to replace the thermocouple. I had a spare that the previous homeowner just happened to have sitting right by the heater. I didn't really know what it was for, but when I was perusing the internet, I found a page that said to consider looking at the thermocouple when a heater won't start. Like most situations, not every heater will be the same but the function of the thermocouple is pretty standard. From what I can tell it's sort of a safety feature. One end of the thermocouple is usually near the pilot light and the other end should connect to some part of the electrical signal flow that controls a magnetic gas valve. The basic idea is that while the pilot light is lit, the thermocouple will allow electricity to flow from the power supply, through the thermostat, then through the magnetic gas valve and back to power to complete the circuit. If the pilot light goes out, the circuit is broken at the thermocouple which will prevent the magnetic gas valve from letting gas flow through with no source of ignition. My heater is about 50+ years old, so a lot of newer ones probably operate differently. But I hope this info is helpful to someone.

[Troy]

Thanks for the information, NotNorm. I am sure someone will stumble upon it and find it helps them with their own problem.


chris_swany, did you solve your problem?


Welcome to the forum!

[philly0128]

I've been looking for a picture of a thermocouple, can someone tell me where I can find 1? my furnace is by "day & night" I'm having the same problems, the pilot is on but it's not sending the heat. If anyone knows of this brand or a site where I can see if I can find the hand book that would be great, i'm coming up empty on my searching.

[NotNorm]

When I was searching the net, I found that thermocouples come in all shapes, sizes and styles. I didn't have much luck in finding a definitive site with great pictures of a thermocouple. Not to mention the number of applications for thermocouples beyond heaters and water tanks. But, the easiest way to locate your thermocouple would be to find your pilot light and look for the "tube" that run from where it is to some kind of electrical switchbox. The main key is that your thermocouple ISN'T going to run back to the gas line. Anything going from your pilot light to the gas line is probably the gas supply line for the pilot light. Again, I'm kind of new at this and somewhat of a "dare devil" as I actually replaced the gas valve on my furnace a few years ago with no knowledge of gas or plumbing. (It was an emergency situation where the gas man came out and disconnected the furnace due to a leak at the valve on a Saturday morning. He left me with instructions on how to install the new valve and I tried it!)

[a46geo]

Thermocouples are all the same. The only difference is the length. They commonly come as short as 12 inches and as long as 42 inches. What determines the size is the distance from the pilot safety to the pilot light. If it will reach, it will work. Most hardware stores carry them. You don't need a photo.

Pilot sensors on the other hand can vary widly. A thermocouple is for a standing pilot, the pilot sensor is for spark ignition. One problem common to a sensor is carbon build up. Gently clean the sensor with emery cloth and reposition it. GENTLY tapping on a pilot, while the pilot is lit will also help clean it. When doing so, the goal is a crisp blue flame. If the sensor doesn't sense the flame, it will not allow the main gas valve to open. This is good! it is doing what it is designed to do.

The Payne/Day Night brand is a United Technologies product and is excactly the same as a Bryant or Carrier product. They are built in the same factory, using the same parts. The only difference is the name tag.

Hope this helps.