Without my brand new inducer motor coming on at all ever when power is turned on my gas furnace starts,igniter starts andlights pilot and then burners light and then big flame blowback like its getting too much gas far too soon...all this happens in 5 seconds or less after power to furnace is turned on.....What is going on here? Inducer motor coming on should be at start of firing sequence but never comes on yet furnace fires up albeit with blowback??
I will agree that something is miswired. The inducer motor is the first thing to come on. The inducer motor is actually sucking the gas through the heat exchanger. Without the sucking the gas just goes where it likes. The gas shouldn’t flow unless the draft proving switch closes. Maybe you got the wires mixed up. The inducer fan should also come on immediately so there is a problem with where it is getting its power. Without knowing which boards and relays you are talking about it is hard to give a more difinitive answer.
Sorry, No offense on first response.
These furnaces operate on a very complicated and sophisticated control sequence. It in driven by a printed circuit board in which it is impossible to trace the circuitry in the field. It evolves an extremely flammable and combustive gas. I have done this very type of repair for years. So I say again with one minor addition, do your due diligence, research and find a competent individual. They are out there. Get some help. I'm behind you 100%. Wish I was there to help.
More information is needed. The board should not start the ignition sequence if a pressure switch is closed. That's how potentially dangerous explosions are avoided. The first action is ventor motor, pressure switch closes. Next, igniter then gas valve, if flame is not sensed within .7 seconds (usually) the gas valve will close. The flame sensing circuit uses impossible (almost) to fool flame rectification to prove safe ignition. The board sends out an alternating current to the burner faces and the flame only allows half of the sinewave to pass through. So if you can simulate a 60 cycle DC half wave 20mV signal you can trick the flame proving circuit. But for the board to even get there with a pressure switch stuck closed is impossible. Unless the wrong board is installed. Or is it an early high efficiency model, like 1980's? They had some unsafe ignition sequences that could lead to a small explosion. Not a home wrecking explosion, just a furnace wrecking explosion. You really shouldn't be fiddling around with your furnace. It'll probably cost you more this way then to have a good tech come out. We do exist.