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What Is model on unit?
OK if you keep a vacuum sucked on the pressure switch will the gas valve open?
Try turning to HEAT, suck on hose and as soon as you hear pressure switch click, check for 24 volts at gas valve
If pressure switch is closing and you hear it click you may have a defective board even though new if board does not send 24v to valve.Try unplugging wires from pressure switch and reconnecting to make sure connections are good so board sees switch is closing.
THat is correct.The inducer is what pulls a vacuum on the switch. Now if unit had been running we might have water backing up preventing switch from getting vacuum, but since this is new, that should not be the case.The board signals inducer to come on,Inducer comes on and pulls vacuum on switch.As soon as switch closes, it signals board to send24v to valve and burners light.As soon as burners light flame sensor signals board it is ok to stay on and energizes main blower.If it fails anywhere along the way we get a fault code. In our case the code is saying switch is still open
It will click when opening and closing.You need to keep a vacuum sucked constantly to keep it closed.
Yes, the board is not sending enough voltage to open valve
1/2" gas line is plenty sufficient unless your meter is over 100 feet away from furnace.But regardless of pressure, gas valve will not open until it gets 24v.If pressure were the problem, valve would open, burners just would not be hot enough to keep flame sensor warm.
Sounds good.Would like to know results