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Rick
Rick, HVAC Supervisor
Category: HVAC
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Experience:  40+ yrs. experience as a licensed oil & gas technician.
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Issue is regarding a lennox g50uh (x), i keep getting a

Customer Question

issue is regarding a lennox g50uh (x), i keep getting a Blocked inlet/exhaust; condensate line blocked; or pressure switch closed prior to activation of combustion air inducer
JA: Thanks. Can you give me any more details about your issue?
Customer: exhaust fan comes on, gives the two fast blinking lights that everything is ok. then goes to the DS2 light slow blinking, and doesn't do much of anything than that and shut off
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Submitted: 10 months ago.
Category: HVAC
Expert:  Rick replied 10 months ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.
This error is either a draft problem or a clogged condensate drain problem. You need to remove all the hose on the unit an make sure the water is draining freely. Also check the small vac tubing connected to the draft pressure switch ( see attached pic for typical). The tubing should have no water in it and where it connects to the furnace should be open. You can poke a paper clip into that port but not the one on the switch.

Customer: replied 10 months ago.
As far as hoses are concerned, the only one is the vacuum tubing connected to the draft pressure switch (unless i require it to be disassembled further, but most of the wiring and it seems all the circuit boards are visible) , and that vacuum hose goes to the exhaust fan. The hose is clear, the exhaust fan side, i am able to blow through. and the switch side i am able to blow and suck and cause it to make a clicking noise. Exhaust pipe did have a couple mud dobber nests in it, but i have cleared it out and it is clear now. The only "hose" for draining condensation is on the upper part of the unit and is PVC and drains down from there to be pumped. it seems to work because it drains my AC just fine. So from here, i dont know what to do, which is why i am seeking the advise of an expert such as you.Thanks Dan
Expert:  Rick replied 10 months ago.

Ok, blowing/sucking on the hose to the switch doesn't indicate anything if it clicks. The vacuum that the switch responds to is far lower than what your lungs can create. So since you're sure the tubing and the port the tubing connects to is clear then you either have a bad switch, a weak draft inducer fan or your vent us still partially blocked. The only way to determine which is the likely culprit is to put a manometer on the exhaust and measure the draft pressure. Since you probably don't have a manometer replacing the switch would be the next thing to try.

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