Payne PG9MAB036080 Gas Furnace issue


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Old 01-14-24, 12:20 PM
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Payne PG9MAB036080 Gas Furnace issue

Furnace works sometimes and doesnít others. Igniter has continuity and ohms at 50. Pressure switch does close as seen by continuity on voltmeter but I can only check it with wires disconnected at startup right? Anyway to see if it stays closed before sending signal to board to turn igniter on?

I am unsure if itís the circuit card or the pressure switch. The circuit card is not sending 120vac to igniter during these times when it doesnít turn on. I do get a 31 fault code.

ignitor has proper ohms, hose from pressure switch to inducer was cleaned with paper clip but didnít notice anything. If I disconnect the pressure switch wires and reconnect, it works. If I bypass the switch at startup, it works also.

 
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Old 01-14-24, 01:19 PM
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Measure for 24VAC across pressure switch when connected

leave the wireís connected.

If connected to the pressure switch 0 volts means closed contacts and 24 volts is open contacts.

You want a reading of 0 volts across the pressure switch when the inducer is running.

 
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Old 01-19-24, 03:41 AM
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Finally had another failure to test. Pressure switch would stay open and didnít show 0V or continuity this time.

I jumped the switch and the furnace functioned normally.

should I replace the pressure switch or check inducer motor?
 
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Old 02-23-24, 08:07 PM
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Same furnace - exhaust pipe has strong smell

My Payne initially had this problem couple months ago. Had service come out and they checked fuel mixture and said it was fine. Said it had cracked heat exchanger but the inside of my home didnít have CO. There is the same smell when I get real close to the furnace but my CO detectors are not going off.

after service left, the smell went away for months now and I started getting the pressure switch issue I originally posted about. I switched out the pressure switch and itís been working great for couple weeks but now this smell started yesterday. Please let me know if you have any suggestions.
 
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Old 02-24-24, 01:50 PM
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Said it had cracked heat exchanger
Either the heat exchanger needs to be replaced or the entire furnace..... ASAP.

Regardless if you sense or measure CO.... it's there.
You need a dedicated CO meter to measure the actual quantity.

The pressure switch monitors the flue condition. Pressure switches are 99% reliable.
You could have a blockage in the flue/exhaust.
You could have a clogged pressure switch connection.
Please read first for furnace repairs.
 
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Old 02-24-24, 03:28 PM
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But the smell went away for 2 months. If it was cracked, not sure that would happen right? I feel like the burners are not burning all the gas.

pressure switch was bad because I put it on my other identical furnace and it stopped working. The exhaust has nothing in it and is short so I can check that.
 
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Old 02-24-24, 03:58 PM
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CO has no smell. It's an odorless gas.
You may have smelled unburned/partially burned natural gas.

You can confirm how well the burners are working by visually inspecting them.
If they are not completely lighting then the burners may need to be cleaned of internal rust.
 
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Old 02-24-24, 04:11 PM
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Yes CO is that odorless. If there were a crack we would get our detectors going off. I have had HVAC folks tell us thereís a crack 4 years ago when water was coming out the furnace. They just wanted to replace it and make $7k. Ended up being a clogged condensation trap.

the smell is a foul but not rotten eggs. Burners look blue and consistent but there is rust around opening to heat exchanger where it blows flames into. Any suggestions on making sure all gas is burned properly?

thanks!
 
 

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