Pressure Switch woes

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  #1  
Old 12-19-13, 07:34 AM
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Pressure Switch woes

Although its a common topic in general I believe I have an interesting question.

The background story to follow, here is the question:
Why does simply blowing/sucking into my pressure switch until I hear it close seem to fix my furnaces... for a while, then I blow into it again to fix again? Is this ruining my pressure switch? I'm thinking not - I don't see how I can damage the diaphragm with my lungs.

This has happened on 2 furnaces now both high efficiency gas furnaces. The first one I ran on Natural Gas, and my latest is Propane. At my old house (a 85% goodman of some sort, natural gas) the manometer showed about .60 WC (pressure switch said .75). I checked all the usually stuff, air flow was fine (disconnected both intake and exhaust), cleaned condensate trap, motor sounded fine. Simply blowing on the pressure switch, hearing it click, and re-attaching would fix it for a month or 2.

This morning my frazer-johnson (G9t10014upc13c) - on LP - had the same 3 blink LED error (its been below 0F here in MN -even during the day - for about 3 weeks straight now).

Manometer reads 1.0 WC (although its homemade and not super accurate), pressure switch says .65. Blew on the lines to the inducer and chamber, blew on the pressure switch (till hearing the click), now its running fine again. I'm thinking I actually do have a bad pressure switch.

Edit: originally i listed that i had a reading of 0.5 inches water this morning, i was only reading one half of my manometer and forgot to multiply by 2.
 

Last edited by skiboarder119; 12-19-13 at 08:14 AM.
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  #2  
Old 12-19-13, 08:48 AM
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Hello and welcome... Hmmm Its possible the pressure switch is sticking... I believe you diagnosed it well and the switches are not they expensive to change...

Possibly condensate is working its way into the switch...

Is the condensate tube installed properly?
Is the flue pitched properly per the manufacturer?
Proper length/size flue and amount of ells?
 
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Old 12-20-13, 05:41 AM
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Update: Once again the truth is pressure switch failure is much less common than a blocked pathway. After it stopped working last night, i wanted to double check one more time. This time the manometer showed an iffy signal (sometimes 1" WC, other times almost nothing). Turns out the nozzle on the inducer motor was plugged, just enough to cause it to be somewhat intermittent. A 3/16 drill bit took care of the problem.
 
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Old 12-20-13, 05:55 AM
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Good job.

Yes pressure switches don't fail that often.....If at all.......
 
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