HVACopediaICP · Furnace
2 Pressure switch did not open
What the control is telling you
A pressure switch was still closed when it should be open (before the inducer starts).
Applies to: ICP F9MAE / G9MAE modulating variable-speed condensing gas furnaces (060, 080, 100, 120 kBtu/h)
Likely causes
- Obstructed pressure switch tube
- Pressure switch stuck closed
Test and repair steps
- Check pressure tubes for blockage or water; clean and shake out.
- Do not blow into a tube while it is connected to the pressure switch.
- Check the switch opens with the inducer off (ohmmeter); replace if stuck closed.
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Source: ICP (F/G)9MAE Service and Technical Support Manual 440 04 4700 00, Figure 16 Troubleshooting Chart, p.34. Summarized in our own words; check the original manual for your model.
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