Hi All, I have an intermittent ignition gas furnace. The pilot flame intermittently will not light. It produces good spark which I can hear and see. The problem seems to be gas supply to the pilot burner. I tried testing for power to the pilot valve circuit on the gas valve assembly using a multimeter. I thought I had power to the valve. However, I may have done the test wrong, or interpreted the results incorrectly, because, I replaced the gas valve assembly, and I still have the same issue. Occasionally when the furnace gets a call for heat, it will produce spark, but the pilot burner does not light. The furnace has a Honeywell S86F ignition control module. Could someone please tell me how to perform a valid test of this module to determine if it is attempting to energize the pilot valve? Any help is much appreciated. Thanks.

I'm in a bit of a dilemma with my high efficency gas furnace. I just had a local heating and cooling company out to check it out and I don't feel comfortable with how it was left. The furnace would heat up, ignite and light, but when the blower kicks on, it knocks out the flame. When the repair was here today, we discovered that it works just fine with the cover off and we began to wonder if the air intake was blocked. He cut into the PVC air intake pipe and we tried to snake it a few times and I even ran some water through it to try and flush out anything that may have been blocking it. We found no blockage of any kind. When he hooked up the air intake pipe again, the flame went out. If we left it unhooked and allowed it to intake air from the basement, it worked fine and did not go out. Has anyone ever experienced anything like this or seen this before? I don't feel comfortable leaving the air intake unhooked as a solution to heat my house but we could not find a blockage anywhere preventing air from coming through. I'm not sure where to go next as another option to fix it correctly.