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Old 04-08-2011, 10:11 PM   #1
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Pressure Switch Question


My heater quit working and the code light says that the pressure switch failed to close. I checked the hose from the flu vent fan to the pressure switch and it is clear. I also blew on the hose that goes to the pressure switch and nothing happened. However, when I did suck on the hose, I heard a click and the burner started.

What does this mean? All of the other posts say that the pressure switch needs positive pressure, not suction. Does this mean that something is wrong or do some switches work different than others?

Thank you!

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Old 04-08-2011, 11:27 PM   #2
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Pressure Switch Question


Draft inducer motor sucks the pressure switch closed IF there is no leak in the heat exchanger. If your draft inducer motor is coming on, it should first in heating mode and it should pull the pressure switch closed, but the pressure switch is not closing then you may have a crack in the heat exchanger.


Last edited by Doc Holliday; 04-08-2011 at 11:39 PM.
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Old 04-09-2011, 10:24 AM   #3
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Pressure Switch Question


OR it may mean your flue is blocked, or the inducer may not be coming up to full speed, or your inducer doesnt work at all, or the press switch is going bad or the port on the inducer where you removed the hose from is plugged.............. It could be any number of things.... Check out the list above. It is almost always never the press switch. Most of the time the port on the inducer is plugged. remove hose, take a small drill bit or paper clip and ensure the the port is clean
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Old 04-09-2011, 11:36 AM   #4
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Pressure Switch Question


Need a manometer to see if it has enough vacuum to pull in to diagnose it properly.
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Old 04-09-2011, 12:33 PM   #5
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Pressure Switch Question


I will check everything that you guys listed (checking the flue is going to suck though ). I did notice that quite a bit of air can be felt around the draft inducer when it comes on. I would imagine that not much air would be felt around the inducer since most of the air should be directed into the flue.

Since I can feel a lot of air being blown around the inducer, does that mean that the air isn't going into the flue possibly because it is blocked?
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Old 04-09-2011, 12:35 PM   #6
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Pressure Switch Question


Post the brand, model and serial # so we know what we are working with. Is it a high efficiency furnace with plastic vent pipes or a medium efficiency one with a metal pipe to the chimney? The inducer has a fan on it to cool the motor and that may be what you are feeling.
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Old 04-09-2011, 11:32 PM   #7
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Pressure Switch Question


The furnace is made by Goodman Manufacturing Company and its model number is GMP075-3 REVB. It also has a metal vent pipe that goes all the way to the roof with a vent cap on it. No work has been done on the furnace since I bought the house three years ago.

I live in California, so no one is going to freeze to death without the heater but it still would be nice to get it fixed .
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Old 04-10-2011, 12:15 AM   #8
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UPDATE!

I was able to clean out the nipple from the pressure inducer and it fixed my problem I tried cleaning it yesterday with a paper clip but I wasn't getting far enough into the nipple. I wanted to use my tiny drill bit but I snapped it just last week So, I used the metal end of a spare flag that is used to mark landscape irrigation. It worked like a charm!

Heater now works and the wife is happy. Thanks for all of your help.

I noticed some questionable connections on the vent pipe that makes me concerned that exhaust may be leaking into my basement (I can't verify that any is leaking though). In the meantime, I have my carbon monoxide alarm plugged in the basement and I will fix the flue connections next week.

Thanks again!
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Old 04-10-2011, 08:52 AM   #9
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Pressure Switch Question


Clean the flames sensor SOON. It should be cleaned once a year with fine emory paper or steel wool. Sits in front of one of the burners and looks like this:
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Old 04-10-2011, 05:35 PM   #10
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Quote:
Originally Posted by yuri
Clean the flames sensor SOON. It should be cleaned once a year with fine emory paper or steel wool. Sits in front of one of the burners and looks like this:
Those GMP furnace often have flame sensor problems because of the style burners they use, they have a kit that switched them to inshot burners because of this problem.
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Old 04-12-2011, 12:47 PM   #11
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Quote:
Originally Posted by Ducthunter View Post
Those GMP furnace often have flame sensor problems because of the style burners they use, they have a kit that switched them to inshot burners because of this problem.
I have no idea if my furnace was converted to inshot burners and can post a picture if it can be determined by just looking at the burners.
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Old 04-12-2011, 05:57 PM   #12
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Pressure Switch Question


Does not matter, sensor needs cleaning anyway as regular maintenance.

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