The furnace is a Bryant model # 394GAW000125. The fan is blowing cold air continuously. The only way to shut off the fan is by shutting off power at the furnace. Pilot light will not come on. The filter is new. The thermostat setting is on heat and at 70, fan is on auto. What's wrong?

I would start by checking rollout switches and high limit. You can bypass these switches strictly for trouble shooting purposes. Never leave them bypassed.

I would start by checking rollout switches and high limit. You can bypass these switches strictly for trouble shooting purposes. Never leave them bypassed.

Thanks, I tried bypassing the limit switch but the fan is still blowing continuously. I am trying to figure out where the rollout switches are. Thanks for your help.

You could also have a stuck blower relay on the circuit board.

Once again, I agree with hvac1000, however, I'm not clear on whether your furnace is firing at all. You say pilot won't light, this makes me think that you have no heat whatsoever. If your furnace has rollout switches, they are located directly above burner assembly, there will be any where from one to three of them, and they will have a little nob in between the electrical spades that can be pushed in to reset them. Can you post a pic of your furnace, and burner area. Lee.

Once again, i agree with hvac1000, however, im not clear on whether your furnace is firing at all. You say pilot wont light, this makes me think that you have no heat whatsoever. If your furnace has rollout switches, they are located directly above burner assembly, there will be any where from one to three of them, and they will have a little nob in between the electrical spades that can be pushed in to reset them. Can you post a pic of your furnace, and burner area. Lee.

You are right no heat. The ignitor is not ticking. Just the fan running continuously. I don't think I have rollout switches. Let me know if the picture helps. Thanks again.

That furnace has a fuseable link but it looks so clean I doubt rollout is a problem. If you would please take another picture of the area right above the gas valve. I think the link is there.

Her is the proof of fuseable link.

Factory manual

http://www.xpedio.carrier.com/idc/groups/public/documents/techlit/ii394g-25-1.pdf

That furnace has a fuseable link but it looks so clean I doubt rollout is a problem. If you would please take another picture of the area right above the gas valve. I think the link is there.

Here is another picture. And thanks for the manual.

Here is a picture above the gas valve. This is what I had bypassed, but the fan kept running. Thanks for you help.

The fuseable link is attached to the right side terminal of the plate that is screwed to the furnace with 1/4 inch hex head screws.

I have provided you with a wiring diagram in the link above. You will need a meter to start your testing to find out why the blower keeps running. Usually that fuseable link pops which cuts the burner because of the flame roll out and that causes the blower to keep running but it could be other items in the circuit. This is the reason I provided the wiring diagram for you so you can test items to see if they are causing the problem.

The fuseable link is attached to the right side terminal of the plate that is screwed to the furnace with 1/4 inch hex head screws.

I have provided you with a wiring diagram in the link above. You will need a meter to start your testing to find out why the blower keeps running. Usually that fuseable link pops which cuts the burner because of the flame roll out and that causes the blower to keep running but it could be other items in the circuit. This is the reason I provided the wiring diagram for you so you can test items to see if they are causing the problem.


Thank you for your time. The info was very useful, I will post when I figure it out.

Got a multimeter and did some tests, it looks like the transformer is bad. I will be replacing it and I will report the result. Thanks to both of you. I am a new home owner, and I had no idea where to start. You gave me the information I needed to fix it. Thanks again.

Well, transformer was bad. I replaced it and now I have 24V coming out, but my furnace is still not working. I have 24V at the limit switch, but not at the ignitor. I changed the control board and the limit switch, still have no 24v at the ignitor. I have learned a lot but I have yet to make this thing work. Any ideas why there wouldn't be 24v at the ignitor? I do not have Vent safety switch. I followed the wires from the board and it only goes to the limit switch. Thanks

Did you test the fuseable link yet?

If that is the limit switch, yes. I tested it for resistance and it went down to zero. I think that is what should happen when it is cold.

The fuseable link is the round item on the wire between the connection to the limit switch and the wire. It may look like a little resistor to you. If that is open it will not allow the voltage to pass to make the circuit.

Obviously I had no idea what fuseable link was, I now know. I will check today. Thanks for all your useful answers. And to clarify my previous post the fan is no longer running continuously. The transformer fixed that. The fan will come on if the tstat is calling for heat, and will stop when the tstat is satisfied. The only problem is I am the one making the tstat go up and down.

It sounds like you have it working.

Yes and no. The fan does what it is suppose to. But, now I have no voltage at the spark ignitor. I checked where the owner's manual said to check for voltage on the gas valve, and there was no voltage. This happens with both the old and the new boards. I think it might be a safety thing but I am stuck. Is it time for a new furnace?

The fuseable link is the round item on the wire between the connection to the limit switch and the wire. It may look like a little resistor to you. If that is open it will not allow the voltage to pass to make the circuit.

Checked the fuesable link and it is good.

Good news, furnace is finally working. I had a pro look at it, he figured out what had gone wrong in about 5 minutes. The initial problem was fixed by the transformer that I had replaced. The second problem was caused by my friend - really. We had replaced the old tstat, and one of the wires was put on wrong. The wire was tagged correctly, but it was put on wrong. Lesson learned - double check your work. hvac1000 thanks for your time and all the useful information you provided.

Glad you got to the bottom of that one. Stay warm.