Inducer Motor

York furnace wont ignite?

My york furnace wont ignite. I turn on the power and the inducer motor comes on and the blower comes on. The inducer will run for about 8 seconds then shuts off. The light blinks 4 times and that says open limit switch. I replaced the limit switch and still the same problem. It is getting power to it. I even replaced the rubber hose to the pressure switch. Could the pressure switch be bad since they are all tied in together and just giving me a false blinking light saying the limit switch is open?

Usually there is a separate fault indication for the pressure switch. It is usually wired separately and not in series with the temp limits. But it could be in series.

I'm not sure what you replaced since you said "the" limit switch. When they say limit switch they mean any of the safeties and I have seen as many as six of them besides the one in the heat exchanger on condensing furnaces.

On a downdraft, fan on top, there is usually one on top of the fan and one in the blower compartment. One on either side of the burners, or both sides. One or more on the front panel.

Easiest way to find them is look at the wiring diagram to find how many and then follow the low voltage wiring around to find them. Most are resettable and have a red button on top that pops out when they trip. Pushing it resets it and the unit should fire up.

Most common one to pop is the one on top of the blower on a downdraft. Dirty filters will leave too much residual heat in the unit and then the safety pops when it shuts down.

Best way to find your open is a meter. Check both sides of the bi-metal safeties to find where you lose your 24 vac voltage. You can put one meter lead to ground. When you find voltage on one side and not the other that is the one that is open.

But you might only have that 8 seconds after startup to do the checking. Shut it off and restart the sequence and check the next one. Repeat.

Good Luck.

Also note some models use a thermal fuse in the wiring to the high limit safety in the heat exchanger that can go open. You can see that device usually within inches of the limit, wired in series.

Sorry I'm not more familiar with the York. I hope that helps.

One more thing. The most common pressure switch failure is not the hose but the fitting where the hose connects to the furnace gets plugged up. A paperclip wire will clear that nipple.

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Furnace inducer motor



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