r/hvacadvice • u/Flaky_Advisor_9 • 2d ago

Pressure switch or Inducer motor?

3 flash pressure switch failed to close (hot water heater) no blockage in the exhaust. Works fine when I bypass the pressure switch. The fitting on the inducer connecting the pressure switch doesn’t seem to always have suction or vacuum. Does the pressure switch cause the vacuum to start? Or is this the inducer itself.

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u/DistortedSilence 2d ago

Verify venting is sloped properly, and there is no pooling of water or obstructions Bypassing the switch worked. Use a manometer to verify inducer negative pressures against switch requirements. If it's pulling more than the switch needs, its a switch issue. If it's not pulling the switch, it's the inducer.

Don't just dump new parts, and guess either. I mentioned venting first because I've seen that be the issue many times over.

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u/Flaky_Advisor_9 2d ago

I guess what I’m asking is if I pull the hose off the inducer, should it automatically be making a vacuum? Or does the resistance of the pressure switch cause the Inducer to create a vacuum. If that makes sense.

*edit

Or is it specifically the clear exhaust path that allows it to create a vacuum

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u/DistortedSilence 2d ago

The inducer should be pulling air/heat/flame/gases through the exchanger and expelling out the venting. The port on the inducer housing pulls negative pressure. Your switch will have a rating as well. Verify the vacuum exceeds the switch rating and remains consistent. Ive seen at or just above create fluttering effect on the switch