Low-heat pressure switch is open while the high-heat pressure switch is closed. The chart says to check the pressure tubing, low inlet gas pressure if a low-gas-pressure switch is used, mis-wired switches, and a low-heat switch stuck open.
Homeowner part this code names: furnace pressure switch hose.
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Bryant 43 means the low-heat pressure switch is open while the high-heat pressure switch is closed. The chart lists disconnected or obstructed pressure tubing, low inlet gas pressure if an LGPS is used, mis-wired pressure switches, and a low-heat switch stuck open. It is not code 32, which is the low-heat switch that did not close on its own, and it is not code 23, which is a switch that did not open.
Likely causes
- Disconnected or obstructed pressure tubing
- Low inlet gas pressure, if a low-gas-pressure switch is used
- Mis-wired pressure switches
- Low-heat pressure switch stuck open
Safe checks for 43
- Count 4 short flashes and 3 long flashes. Do not swap the pressure-switch hoses to see what happens
- Techniciancheck tubing, switch wiring, and the low-heat switch. Gas pressure, if an LGPS is used, is part of that check
Capacitors can hold a charge after the power is off. Safety terms.
When to call a pro
Call a licensed HVAC technician. Two pressure switches disagreeing is not a vent-cap cleaning.
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Parts & tools for this fix
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Furnace pressure switch hose: guide
In this code: Disconnected or obstructed pressure tubing
See the guide for what to look for when buying one.
Furnace pressure switch: guide
In this code: Low inlet gas pressure, if a low-gas-pressure switch is used
This one is for a technician to test or replace, so we only explain it and do not link to buy it.