# Furnace won't run with blower cover on



## Solex (Jan 7, 2015)

Hello there
We have payne furnace and it wouldnt work with blower cover on. Flashing code 33. Installed brand new blower capacitor, cleaned exaust duct. Checked flame sensor for resistance. High limit switch. Still nothing. When trying to install lower blower cover it seems like it going to sucked it right in. My question is: Inducer fan comes on for about 45 seconds and then flame, blower as soon furnace started working it shuts off and inducer blower fan stoped working as well.
Shouldnt inducer fan be on at all times to expel exaust gases. Thank you very much
Solex


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## BigJim (Sep 2, 2008)

Solex, I started your own thread, you should get more response this way.


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## yuri (Nov 29, 2008)

The normal sequence of operation is the thermostat sends power to the W on the circuit board and you should have 24 volts from there to C when it is calling for heat.

The inducer must staying running all the time when that happens. If you have a steady 24 volts and the inducer stops then the circuit board is bad. There were a lot of problems with the older boards having bad solder connections on the back. Boards and relays fail with any brand. Sounds like yours is dropping out for no reason. If it stops the fan mid cycle then it will overheat and give you that code.

Make sure you have a steady 24 volts from W to C or else the thermostat is faulty.


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## Solex (Jan 7, 2015)

First of all:Furnace blower keeps runing titlle is NOT my posting. My posting was furnace WONT run with blower cover ON.
I am asking simple question and expect simple answer if anyone know.
Thank you


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## Solex (Jan 7, 2015)

Hi Yuri
Thank you very much. Finaly i am geting somewhere. I was going to check pressure switch voltage, but i would need ohm-voltmeter, for which i dont have. Its cold in here, Guelph Ontario Canada -21c. My concern is when thermostat reaches set temp. say 22c it goes in lock mode and flashes 33, till cools off and then we have steady red glow light.


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## yuri (Nov 29, 2008)

33 is open limit. Sounds like you have an airflow problem and it should not suck the door closed very hard. Make sure nothing is blocking any of your return ducts and the filter is clean. Make sure the heat vents are open and not blocked by furniture etc.

Some people have these extra filters that drop in the return vents at the floor level and forget they are there and when they plug up problems happen like reduced airflow.


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## Solex (Jan 7, 2015)

I am suspecting pressure switch, checked hose to it,mouth blow true it and its free off obstruction. I would need ohm-voltmeter to check it if is working ok'. It should read 24 volts. This pressure switch has 2 conectors, one lead is going to exast limit switch.Also checked out exaust limit switch. Somehow furnace is working ok, no flash code. Still runing with damn blower door off. I am not giving up. I have G3 licence, too bad that i couldnt' pass exam for G2. I love this stuff and yet i am in machinist industry for past 30 years. Thanks a lot Yuri. It takes a lot from you to share knowledge you worked so hard for.


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## yuri (Nov 29, 2008)

Yur Welcome. 

Running with the door off is giving it extra return air and has nothing to do with the pressure switch. There is a seperate code for that. Sounds to me like you are not getting enough return air. If you have air conditioning check underneath the cooling coil as it may be dirty and obstructing the airflow.


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## beenthere (Oct 11, 2008)

Its not a pressure switch issue if its running okay with the blower panel off. You have low air flow. If you have A/C, it could be that the evap coil is too dirty, and restricting air flow.


PS: Fixed the thread title for you.


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## Solex (Jan 7, 2015)

Very thank you very much guys. This furnace is located in crawl space, and suply duct is bent at 90 degree (almost touching floor joists) right above AC A coil. I was even contenplating to install small fan to suply extra air. Sadly whole crawl space is plenum for there is no fresh combustion air suply (from outside of course).
I am very happy that this whole ordeal comes to an end.
Thank you both guys
Best Regards
Solex


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## roughneck (Nov 28, 2014)

How did it come to an end? What did you do to fix it?


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## ben's plumbing (Oct 6, 2011)

well there you go:huh::huh::huh::huh:


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## Solex (Jan 7, 2015)

It came to final by furnace working without blower cover. Checked all air returns and only one is actualy "sucking" air. I know from my home inspection days that when you place bathroom tissue against return air grill, tissue should stay on it (grill)
Thats double wording in same sentence. Have to find blockage in air return but of all, i have to double check if this one is reverse blower, for motor is. Maybe its from previous owner wrong blower direction. If it is blower runs at aprox 30% capacity
Hope this help


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## roughneck (Nov 28, 2014)

So is it running with the blower door off right now?


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## Solex (Jan 7, 2015)

For now yes, furnace is runing without blower cover. I bypassed door switch.


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## yuri (Nov 29, 2008)

You can suck fumes from the burner into the house so that is dangerous and not recommended.


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## roughneck (Nov 28, 2014)

Be careful doing that. It can create negative pressure and potentially mess with the burners/combustion air.


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## Solex (Jan 7, 2015)

I didnt mean to use it as permanent solution. I will try to find where return or suply air is partialy or fuly blocked. What bafles me is beside blower motor replacement and capacitor, nothing else changed. I took inducer fan of its place and vacum all soot etc. For one reason or other induced fan started working couple days latter. I will reinstall blower cover ASAP. I am still suspecting pressure switch.


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## yuri (Nov 29, 2008)

We are trying to teach you that the pressure switch has nothing to do with airflow. All it does is prove that the inducer is running.


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