Well, here is another question related to my OLD carrier furnace. Again, it is a 58DXA060-101GG (or 100GG.) The issue is that during the day it seems to do pretty ok as far is starting a heating cycle. At night/early morning it seems to be a different story. The thermostat will call for heat, the inducer motor will start up. After a pre-determined time (1 minute?) it shuts off. The thermostat is still calling for heat. If I power cycle the system either from the thermostat or the circuit breaker, or furnace blower door switch, it will run the cycle again and 9 out of 10 times it will continue as normal. Sometimes during the day/evening it will do this as well. But usually we wake up to a house, set to 68-72, and it is 62-66.

I have replaced the pilot once before (3-wire spark pilot), and it still had the issue. I replaced the ignition lockout control, still same issue. These 2 items were "diagnosed" as issues by an HVAC repair person. Obviously they were not the solution. I can't make the furnace replicate the issue, because when I power cycle to test the furnace, it "resets" and works fine. If I don't power cycle, the furnace stays in lockout and I can't take any readings.

I really don't want to throw money replacing parts in hopes it fixes it. My next parts on the list of possible problems are the main control board and the gas valve. I have read similar issues on other sites that people replaced the main control boards and that solved the problem. The furnace is so old that it doesn't have and LED or other indicator to show an error code. So that option is out. Also no flame sensor in this furnace as the 3-wire pilot is a b-metal switch that acts as a flame sensor. Any suggestions?

My plan was to buy the control board next. It looks like the new replacement versions have LED lights, which could help in the future.

Other observations include: Spark igniter will spark for an extended period of time sometimes. Pilot light will sometimes "sputter" and the igniter will spark again to re-light.

  • I also forgot to mention...last weekend the furnace decided to do nothing at all. I could get the relay to click on the main board when I pressed the door switch and let it out. But nothing more than the relay clicking. This has also lead me to believe the main board could be an issue. – Jeff Cates Jan 24 '17 at 0:11
  • FWIW: I had similar problems on my old Lennox which were diagnosed by the HVAC company to be the ignitor module. I have two dead ones now. The last time, the tech said that they will not replace the OEM Johnson Controls anymore, but the generic Honeywell replacement is more reilable. The box says: S8610U 1003 Universal Replacement Intermittent pilot Module. – DaveM Jan 24 '17 at 2:04
  • My Carrier gas furnace is now 25 years old and working fine. About 3 or 4 years ago the furnace would not work. The heating and ac repair service that I use said it was the control board and I authorized replacement. That fixed the problem. Maybe 5 years before that the hot surface igniter wouldn't glow and so wouldn't ignite the gas. A new igniter fixed that. – Jim Stewart Jan 24 '17 at 4:36
  • @JeffCates Does the pilot light when the furnace doesn't work, or does the igniter just continually spark until the unit shuts down? – Tester101 Jan 24 '17 at 12:00
  • When it sparks, it eventually will light. Once it lights, the furnace continues as normal. It seems to be an issue with it being cold. The AC unit works just fine in the summer, so the control board working the main blower works, but may not be working right for the furnace side. – Jeff Cates Jan 24 '17 at 14:14

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