I have an old (14 years ?) York Stellar furnace that used to have this problem sometimes. When the gas was released over the red glowing electric igniter, it would ignite with a more or less loud pop that would also kill the flames. Then it would go again through the whole sequence and everything would work fine. A couple of times the pop was almost like a mini explosion that made our floor vibrate. A technician looked at it a while ago and said it works fine and maybe there is air in the gas pipes.

Yesterday the unit stopped working. Only the first fan would start and the electric igniter does not become glowing red. The gas is not released. I tried this several times and the only thing would start was the fan. We called a tech and two hours later when he came and started it, the furnace worked fine. He suspected some intermittent contacts and while he was measuring voltages the furnace stopped working again. He found out no voltage was present on the electric igniter, so he said the “module” must be the culprit and it’s a $400-500 job to replace it. He also said we might better think about replacing the whole furnace because this old unit we have will keep having problems and repairs are costly.

We decided to think about it and he left without doing anything. The furnace was not working when he left. Later in the evening I turned it on again and worked fine.

To summarize there are two issues: the loud pop that sometimes happens and the intermittent malfunctioning.

Any thoughts?

Thank you,
Cuptor

It could very well be a module but I cannot test it from here. The loud pop could be caused by a bad module not allowing the gas valve to open properly.

At 14 years of age you might consider a new 95% efficient furnace instead of spending $$ on fixing the old.

Maybe before giving up and replacing the furnace, check the connections to the ignitor and module.

As far as the popping sound, you may need to adjust the gas pressure, it may also be the control board not bringing the HSI on fast enough therefore it's building up too much gas, either way if the furnace is only 14 years old it still has a few good years left, I'd seek a second opinion, it kind of sounds like the technician may be doing a little too much guessing.

hvacservicetech_07 ,

What is HSI?

Hot Surface Ignition

There are many types of pilots and ignitions

Standard Standing Pilot

Millivolt system

Intermittent Pilot

Glow Pilot

Hot Surface Ignition

Direct Spark

I watched many times the ignition sequence and I think the HSI timing is OK. It gets red and few seconds later when I hear the gas starting to flow and the flames would start right away. Rarely the little pop/explosion would happen and this would terminate the flames and then it would go again through the whole sequence.

Now I remember another thing the tech said it might be. He said only one gas injector blows over the electric igniter and it might accumulate dirt, so its flow would be weaker and by the time it pushed enough gas over the hot igniter, there is already a lot of gas in the chamber coming from the other injectors and when the flames start it would explode.

Regarding the furnace stopping working I need to say it keeps working now since Sunday evening.

I hate intermittent problems.

I am an electrical engineer and could check some things smyself (I have no schematic though), but I am concerned of not messing up something in the gas flow.

The sequence of operations in the sticky at the top of the forum might help too. I think there are links to furnace manuals too.