Any heating and cooling Guys out there? I have a question
Ceramic only for a HSI system, his is a spark ignition, .
I don't get what you are saying here. Hot surface, flame sensors, and spark ignition electrodes are all mounted in ceramic insulators/ mounts. What I was getting at is that the sensor wire can sometimes come loose internally and lose reliable connection.
These are wired in a series one locked out or not functioning and it would not fire. Trouble shooting skills 101. Its sparks , it lights...doesn't stay lit, so all else is good, it will be flame sensor seeing no flame after being lit (mili seconds after) or back to the board where this is all times out via PC board. .
I'm speaking more of an intermittent problem. An example is a shakey vent barometric switch, or a vent problem "right on the edge" causing the switch to dance in and out. I've seen both. What can happen (with inexperience) is that the burner may light for just a moment, and the "puff" is just enough to trip the baro switch offline.
I've learned, over the years I worked on this ****, not to make assumptions. I also, as a rule, never "threw parts" at a problem. But vent barometric, and vane and other duct pressure switches, frankly, can be a real PITA.
When I was doing this stuff, many controllers did not yet have diagnostics. Some of the old crap like the GE rooftop units had "relay logic" that was more than a nightmare.
Another one I hated, and we had a few thanks to a long gone contractor, was an odd electric furnace I can no longer remember the name of
They used "Pi rod" type heater elements, and DC control circuits. When they worked, they were fine. When they started to give trouble, they were ridiculous. This was before Al Gore invented the internet.
One of thes, I actually pulled the controls out, and converted to AC controls with plain ol' heat sequencers. Took longer 'n I thought it would, and we made no money on that deal.
Some of the old Honeywell flame rod based burner controls for the big "gun" 200-400K BTU rooftops was absolute crap when it gave trouble.
I just last month had to order a new board for my Carrier 80%. The good news is that there are now aftermarket boards that are a lot cheaper than Carrier wants to rip you for. This is one good thing about the internet.