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HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
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Experience:  15yrs in the HVAC industry with certificates and degrees.
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My gas furnace won't fire up. It sounds like the initial

Customer Question

My gas furnace won't fire up. It sounds like the initial purge blower starts up but the ignitor doesn't glow and the blower fan runs like nothing is wrong. The led blinks once in repetition which indicates air flow fault. I am searching what causes the airflow fault
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Submitted: 9 months ago.
Category: HVAC
Expert:  airheatman replied 9 months ago.

Can you please give me model on furnace so I can give answers and guidance specific to your furnace?

Model will be on a label just above burners on right or left inside panel

http://i.imgur.com/U8b0GXT.jpg

Expert:  HVAC Guru replied 9 months ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset I am just one of the techs on here and I try to get to as many customers as I can and I just picked up your question now. Please allow time for me to respond, sometimes I get the questions or responses late so please be patient as I have no control over the site issues. NOTE, I have nothing to do with your payment to the site and did not receive that money. You have to supply a rating in order for us techs to receive credit for our time as we have nothing to do with any payment made to the site.

ANSWER:

That issue means that there is a pressure switch error when the inducer motor starts to run it pulls a vacuum through the rubber tube attached to the inducer blower housing. Check that port for any blockages. Pull off the rubber tube and see if there is anything blocked in the port where the tube connects. Often stuff gets clogged in the port itself causing that issue. Check the rubber tube as well to make sure it is clear and free of any cracking or dry rotting. Also check the exhaust port at the outside to make sure nothing is blocked on the vent tube outside your house. If all that is good you need to check the pressure switch itself as that may be bad and not working properly.

Customer: replied 9 months ago.
It is a Magic pak 51HW242A-9B.
Customer: replied 9 months ago.
Here are the photos
Expert:  HVAC Guru replied 9 months ago.

Yes you need to check the pressure switch circuit.

ANSWER:

That issue means that there is a pressure switch error when the inducer motor starts to run it pulls a vacuum through the rubber tube attached to the inducer blower housing. Check that port for any blockages. Pull off the rubber tube and see if there is anything blocked in the port where the tube connects. Often stuff gets clogged in the port itself causing that issue. Check the rubber tube as well to make sure it is clear and free of any cracking or dry rotting. Also check the exhaust port at the outside to make sure nothing is blocked on the vent tube outside your house. If all that is good you need to check the pressure switch itself as that may be bad and not working properly.

Customer: replied 9 months ago.
Unfortunately, The tube is very difficult to reach on the inducer motor side. This is a compact magic pak in a condo unit. The pressure switch side of the tube seemed fine. I'm not sure how to proceed with the inducer side though.
Customer: replied 9 months ago.
Is it difficult to remove the inducer motor? It looks like a bit of trouble to remove, tight spaces, etc.
Customer: replied 9 months ago.
Or is it more cost effective to replace the pressure switch and see if that works?
Expert:  HVAC Guru replied 9 months ago.

Replace the pressure switch first as the blower is working and running just make sure the port is clear where the tube connects to the exhaust blower. Other than that try a pressure switch out and also make sure the condensate drains are clear and draining.

I would like you to know that I am a tech that works for the site, the payment you made to the site is not automatically credited to me nor do I receive all of the payment you made. The only way I receive any credit at all for my time is by you selecting a STAR using the 5 STAR RATING SYSTEM on your page before you leave. If you are not happy with the service please let me know before leaving a negative rating. This will also allow you to get directly back to me for FREE follow up questions and tips are greatly appreciated! Thanks

Customer: replied 9 months ago.
From the inducer motor picture I sent, does it look like it may only be held up by the two top screws? I'm wondering if I need to go through the trouble of removing that motor assembly in order to check the tube on that end and the opening into the inducer.
Expert:  HVAC Guru replied 9 months ago.

Yes I would as that is the most common and likely issue of blockage

Expert:  airheatman replied 9 months ago.

Pressure switches fail, but more times than not,There is another issue keeping it from closing.Before just starting to replace parts, remove the hose and make sure it is free and does not have a split where it connects to inducer.Go to the trouble to remove the inducer if you have to ands look inside to check that there is nothing blocking the port such as carbon build up , that little blower wheel is in tact and that nothing is inside effecting vacuum.I have found small birds and lizards inside.

Customer: replied 9 months ago.
There are just two looks like sheet metal screws holding up the inducer motor. Can that be all that's holding it up?
Customer: replied 9 months ago.
I have removed the inducer motor. The area is clear and I can blow air thought the vacuum hose. What should I look for next? The port to the outside is clear as well.
Customer: replied 9 months ago.
Ok, Here's what I've done. I reinstalled the inducer motor, Blew into the hose leading to the pressure switch to actuate it a couple of times, none of that worked. I then jumped the pressure switch leads and then the furnace fired up. I assume this means the pressure switch is bad. Is that conclusive? Or could it still be something else. This unit is about 15 years old if that matters.
Customer: replied 9 months ago.
Anyone there? I bought a new pressure switch with a different design but the same rating and replaced the old one. The furnace still does not fire. Any other suggestions? I can still get it to fire if I jump the pressure switch leads.
Expert:  airheatman replied 9 months ago.

That is what I suspected while other expert who jumped in kept telling you the switch was bad and begging for you to pay him.Pressure switches are rarely the problem,Usually something preventing switch from closing.

I see the inducer looks pretty rough.How was the gasket where it mounts to furnace.May be leaking there.

Expert:  HVAC Guru replied 9 months ago.

You either have a bad pressure switch or like I posted earlier a blockage of some sort. Now the pressure switches can be damaged by blowing through them as well, you can only very gently suck a small amount of air through them for testing. Secondly if the exhaust fan is coming on and blowing good air out the vent outside I would double check the hose port and even blower itself for any issues. The fan could be bad and not blowing enough air, the housing around the van could be rotted through or a shaft seal could be bad, but other than that there is not too much else that would cause this issue. I am sorry you are dealing with two techs here, just note I am HVAC_GURU and when you choose to rate a tech just make sure you choose which tech you want rated as that is the one that receives payment and credit and there can be only one rated.

Thanks HVAC_GURU