I have a carrier furnace. Pressure, draft safeguard, or aux limit switch did not close or reopened. This is what my furnace is blinking as a LED code. What should I do? My furnace does not turn on. The manual saysIf open longer than five minutes, inducer shuts off for 15 minutes before retry. Check for - Proper vent sizing and condensate pitch - vent restriction or hight winds - defective inducer motor or stat capacitor - defective prssure switch or connections. If it opens after trial for ignition period, blower will come on for 90 sec. recycle delay. - Inadequate Combusion air supply - low inducer voltage - disconnected or obstructed presure tubing. We had someone come out and replace an ignitor . The unit will come one once in awhile when the house is warmer. Sometimes the air is cool. Most of the time hot. The thermo is set at 71 but the house only reaches 61 - 63.
The limit switch on the inducer has tripped. There are two wires that go to a small disk about the size of dime that has a small button in the center. Push this little button and you will feel a littl snap and the unit should fire up. Check all the manual reset limits as well. If the unit still won't start, jump the two wires by bypassing the limit switch. If it starts, then replace the switch. Bypassing the switch is only temporary and could lead to death if it is used as a permenant fix.
Where is the limit switch located
Very helpful. My switch had tripped. Once i reset it fired up. Thanks. What could cause this switch to trip?
1. Thermostat calls for heat.
2. Draft inducer motor starts.
3. Pressure switch attached by a small plastic or
rubber tube senses the negative pressure produced by
the draft inducer and closes.
4. Draft inducer runs for 30 seconds to a minute
before you hear a gas hissing sound. The ignitor did
not glow, the flame sensor (a small metal probe about
1/8" in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops
with no ignition of gas to heat your home. Your
furnace shuts down and goes into a lock out condition
until you turn your power switch back off and on
again. Then the sequence starts all over again with no ignition of the
gas.
Solution: You
probably need to purchase and install a new ignitor. I would suggest that you
inspect your ignitor closely for cracks. Make sure
you do not touch the ignitor with your bare hands. If
you do not visually see a crack, then you could have a furnace control board
problem or a limit, rollout switch problem. Please see "limits, rollout
switches & furnace control boards" further down on this page. The furnace's
control board might not be supplying the voltage to the ignitor. If
your furnace lights and the gas stays on for 8 to 10 seconds, then shuts right
back off, then you need to clean your flame sensor with light sand paper or
steel wool. You might need a new flame sensor, but most of the time they can be
cleaned an will work well after cleaning.
1. Thermostat calls for heat.
2. Draft inducer motor starts.
3. Pressure switch attached by a small plastic or
rubber tube senses the negative pressure produced by
the draft inducer and closes.
4. Draft inducer runs for 30 seconds to a minute
before you hear a gas hissing sound. The ignitor did
not glow, the flame sensor (a small metal probe about
1/8" in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops
with no ignition of gas to heat your home. Your
furnace shuts down and goes into a lock out condition
until you turn your power switch back off and on
again. Then the sequence starts all over again with no ignition of the
gas.
Solution: You
probably need to purchase and install a new ignitor. I would suggest that you
inspect your ignitor closely for cracks. Make sure
you do not touch the ignitor with your bare hands. If
you do not visually see a crack, then you could have a furnace control board
problem or a limit, rollout switch problem. Please see "limits, rollout
switches & furnace control boards" further down on this page. The furnace's
control board might not be supplying the voltage to the ignitor. If
your furnace lights and the gas stays on for 8 to 10 seconds, then shuts right
back off, then you need to clean your flame sensor with light sand paper or
steel wool. You might need a new flame sensor, but most of the time they can be
cleaned an will work well after cleaning.
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