I have a few year old GMNT I installed myself and had checked out by a pro installer so I know it was installed properly. The burners recently started making noise a few minutes after lighting up. Today when I came home the furnace was in lock down and after power cycling it, the burners wouldn't light. Turns out one burner was over heating and melted the wires for the flame sensor and igniter. I have since repaired the wiring and moved them off the top of the burner cage, but still have the issue with the hot noisy burner. Would this be a deposit issue with the burners that a cleaning should fix, or would it be the tube in the heat exchanger itself causing this? This is a GMNT 120-4 98% efficient furnace. Aside from the noisy burner it is running fine, but the fact it melted the wires has me concerned. One of the flame sensors had also tripped.
It is a GMNT 120-5. I tore down the burner assembly this morning and cleaned them all up, then found the flue collector has a crack in it right down the middle to the blower. I tore that off, cleaned it all out, got some high temp silicone and sealed the crack, blew out the tubes in the exchanger, and put it all back together, sealing the flue to the exchanger with fresh silicone on the old gasket. Started it back up and smiled because it was quiet, that is until the main blower kicked in and it started rumbling again. It appears the 3rd tube from the left is getting air in it from the blower. The furnace was installed in 2002 so it is still under the 5 year parts warranty and lifetime heat exchanger, but I installed the furnace myself, so I dont know what to do to get a replacement without having to first teardown the furnace and ship the old one back and wait for a new one in the winter, gets mighty cold here.
I have a friend who does HVAC, he actually moved the A coil for me to the new furnace off my old one when I installed this one and checked my other furnace install and OK'd it for me. I haven't talked to him since 2003 when he was here last time, I will give him a shout and see what he can do. Replacing it myself doesn't seem to be a problem since I darn near go everything in front of it off this morning while cleaning and repairing the flue cover. Doesn't hold up well for Goodman/Janitrol when the HE doesn't last 5 years. Our old house had a Lenox Pulse installed that only needed one repair in 15 years, and that was a relay that I was able to get just about anywhere, and I heard the pulse furnace had problems, but not the one we had.