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servtech50, HVAC Technician
Category: HVAC
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Experience:  over 20 yrs. experience
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I have an older 320AAZ Bryant furnace in the house I just moved

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I have an older 320AAZ Bryant furnace in the house I just moved into and there's a couple things I can tell aren't right with the furnace. When the thermostat calls for heat the blower (for the heated air through the house) kicks on IMMEDIATELY and it blows cold air until the burner is able to warm up enough.. then within a minute or two when the house wamrs enough it shuts down the furnace and the blower also goes off immediately. I always assumed that the burner comes on FIRST and then once the plenum is hot enough the blower kicks on and then when the thermostat is warm enough the burner shuts off and then the blower continues for a minute or two.. correct??? Another thing is that the blower "surges" dramatically.. it sounds like "weeeoo.. weeeooo" and the air goes "whoosh.. whoosh" through the ducts and registers.. I KNOW this is NOT right. Also, there's a red light on CONSTANTLY whenever the furnace is running.. from what I was able to find online.. this means the furnace is in "emergency heat mode"????? thanks in advance for any and all help you can give me on this.. I'm a double master ASE certified mechanic so.. I am very much able to fix this myself.. if.. given the system information/troubleshooting ..
What model thermostat do you have. Russ
Customer: replied 5 years ago.

It's an Honeywell old mercury type.. I just checked the fan auto/on switch again when I was looking at the make of the thermostat and now I notice that the fan DOES come on when it's switched to "on" and the fan runs at what seems like a normal speed too.. a more gentle speed like you'd have during the heat operation.. I know when you sitch the fan to "on" it SHOULD turn the fan on high speed like the speed it uses when in A/C mode.. but.. like I said.. it actually seems to run at what would be the heat mode speed.. so.. it's "bass ackwards".. lol


I have a digital thermostat that I can install and was planning to.. but I wanted to figure out what's going on with the furnace first.. it's starting to point towards the thermostat and/or wiring huh? Either that or the microprocessor in the furnace? Even if it IS the wiring and/or thermostat.. why would it be surging so much? I'm guessing the blower motor is going up and down by about 1000 rpm.. it's enough to make the lights dim and then go bright.. I'm tempted to take out the pleated media filter and leave off the cover and then run the fan to see if it's a supply issue.. to me it seems like there might not be enough air returns either.. OR.. the variable speed controller is shot??

hello, I am servtech 50 and I will try to assist you today.

What you have is one of the first "I" furnaces made by carrier. If someone has been operating this furnace in emergency heat then there is an issue with normal operation of the furnace. We need to find out what that problem is. I am not sure and I see you have already looked the furnace up on line, so you need to find out witch dip switch will take this unit out of emergency heat and switch it off. the dip switch is located on the main control board in the blower compartment. What the emergency heat does is bypass ALL safety switches ramps up both motors...ID motor and blower motor and operates the furnace. So if you can locate the dip switch turn off.... and try to cycle furnace. you, more than likely, will get another fault code, the most common for that furnace was code #44. But before we get ahead of ourselves turn off em. heat and cycle unit. servtech50

servtech50, HVAC Technician
Category: HVAC
Satisfied Customers: 322
Experience: over 20 yrs. experience
servtech50 and 3 other HVAC Specialists are ready to help you
I do appreciate the accept but we are not finished yet, I hope. So please let me know who things are going and after firing your furnace with em. heat off let me know what fault code you have so we can get this unit back to operation. servtech50
One more piece of information, because of the age of the furnace, and you can find this out by serial # the first 2 numbers are the week of the year your furnace was made and the second is the year it was made. i.e. 2888A23456 example this furnace would have been built the 28th week of 1988. Any ways some of those parts to your furnace are no longer available and what parts are are very expensive. servtech50
Customer: replied 5 years ago.
Ok.. I flipped the emergency heat dip switch to off (so someone DID manually set it to that) and it first turned on the blower and circulated air through the house.. then that shut down and then the exhaust blower came on for about 1 minute.. then the pilot light came on for about 1 minute.. then the burners kicked on for a couple minutes.. then the main blower came on at what appears to be the normal speed with no surging.. it is also flashing a code 44 blower calibration fault.. so.. is that the correct sequence and how do I recalibrate (if possible) the blower? Is that code referring to the exhaust blower or the main HVAC blower?

ok, yes every time the main power (120 vac) is turned off then turned back on it will run blower for 90sec. only if there is still a call for heat at that time, otherwise it just turns on.

So yes all that happened is the correct sequence. No the blower can not be recalibrate, it has to do with the conversion from AC current to DC current inside the the back of the motor. You will need to purchase a new one. Be prepared it will be costly, and do not be surprised if you can not even get one. It would be a HUGE help to you if you know someone that will get this blower for you at cost. I am not sure if it is for the main blower or the draft. check code #42. see if that code mentions the draft or pressure switch. if so then it is your main blower. servtech50. PS. if it turns out to be the draft blower out of calibration let me know because there is something else to check before ordering a new draft assembly.

yes #44 is the main blower. All you can do is make sure there is a clean filter in furnace or filter box. And make sure there are nothing blocking return air. if everything is clean and clear you will need a new blower motor. Thank you for allowing me to help you. It has been a real pleasure. servtech50
Customer: replied 5 years ago.
I have been checking everything over and when it runs it's constantly flashing the 44 code.. I flipped the dip for the fault code read out and it does show a code 42 then.. but the furnace is not running during that readout.. so.. is that code being displayed from memory?? I really DO believe that the returns are insufficient.. that was one of the first things I noticed about ths house.. there's only a couple returns but there's a lot of supplies.. BUT.. wouldn't it NOT show a 44 when the blower cover is off and it's drawing air from the basement and hardly any through the returns?? It has a media style pleated filter installed that is brand new and not a paper type either.. so.. I'm pretty sure that the filter isn't restricting the airflow.. I also opened up ALL the supply baffles in the ductwork and at the registers too thinking maybe it was setting the code due to it fighting against the supply side.. but.. it still shows 44.. will having it flashing a 44 all the time eventually cause it to shut down? The blower seems to be working fine and running at normal speeds..
Customer: replied 5 years ago.
I forgot to answer your question about the date code.. it was built in June of 1993. Also, I have been searching all over with no luck trying to find the dip switch default and/or correct settings for my furnace. I have the feeling that since someone set the dip to emergency heat.. they may also have switched some of the other dips.. should all the dips be OFF except for the "NAT/LP" being in the NAT setting? I'm assuming that switches it from natural gas to LP and I run natural gas.. I do believe that the MZ switch is in the ON position too.. and.. isn't that for "multizone" which this house does NOT have.. also.. the previous tenants completely removed the bypass style humidfier and blocked off the openings with sheet metal.. I think there's a switch for if you have a bypass humidfier too.. that should be set to OFF now correct?? I'm hoping that the reason it's setting the 44 code is because of it "thinking" that it's a multizoned system and/or still is bypassing through a humidifier.. which neither are the case.. please let me know what the DIP settings should be when you get a chance.. thanks!

#42 was probably from memory so I would not worry about that.

I am not sure if it will shut down or not. Have you allowed it to run a complete cycle? it will be on a low CFM and after approx. 10 to 12 minutes should ramp up to a faster speed along with the burners should kick in 2nd stage and the draft motor should also ramp up. Most of the dip switches have to do with the delays before and after a call for heat or cool. but I will see if I can locate the information. Humidifier has its own terminal + common at the low voltage terminal strip.

I am on my way out to take my son to dinner, I will check your questions and try to locate info. tomorrow. Have a good night and we will meet here tomorrow. servtech50

Customer: replied 5 years ago.

I think I've zeroed in on it a little more since my last post.. I found that it will NOT set a code 44 if the filter is taken out and.. the filter housing cover is left off allowing it to craw air straight from the basement. I thought at first that maybe the brand new filter was too restrictive but then I found that it still set the code with the filter completely removed but the filter housing cover installed.. that lead me to believe that the supply dictowrk was/is the problem.. I found two "covers" on the cold air return ductwork that someone had covered up with sheet metal and I removed them to see if allowing more air into the return ductwork would allow it to run without setting the code.. it STILL set the code even with those opened up.. and they were drawing serious air through them too. I did find that one of the return ducts goes "nowhere" and it appears that when someone did remodeling in the kitchen they decided that the return duct wasn't needed. In all.. there's only four 12" returns for the entire 1600+ sq ft house and there's at least 6 supply registers.. but.. why did it still set a code when I opened up those patch covers in the return ducts? I'm starting to think that the motor has never been lubricated so maybe the bearings are dragging.. OR... that thermsistor I've read about in the motor is bad.. and one or both of those issues are what's causing it to be overly sensitive to any restrictions at all?????? I did find that the dips were set to MZ (multizone) ON.. and also BPH (bypass humidifier) was ON.. so.. I set them to off and it didn't make any difference. Right now I just took a "cheapo" 1" filter and layed it across the media filter housing opening where the cover goes to filter the air a little bit from what it's taking from the basement.. it's working normally like that.. so.. we'll see if it acts up during the night.. hopefully not..

It is normal practice to take the return out of kitchens, because of the cooking smells and the air born greases, not wanting them to enter the furnace. So did your blower go into second stage speed? I do not think there are oil ports on the motor. I do not remember any in the past. It has been along time since I have seen on of theses furnaces. Let me know what happens. servtech50
Customer: replied 5 years ago.

I didn't see anyplace to oil it either but I did notice a maintenance sticker on the blower housing that says to oil at least every five years when in intermittent mode and if run continuously oil every two years.. so.. I'm assuming there must be somewhere you can oil it.. I can always pull it apart and do it right too.. I'd like to double check the condition of the thermsistor I've read a lot about failing too.. I have a hunch it might be bad or marginal and that could be what's causing it to be so sensitive to any restriction in airflow..


As far as the second stage .. it does go to high heat mode after about 8 minutes or so.. so.. it is working properly.. no codes set overnight.. BUT.. that's without it being filtered and also with a huge diversion of air straight into the blower directly from the basement.. I can't and won't leave it like that.. this basement used to have dogs living in it and there's no way healthwise I'll leave it open like that.. plus.. obviously.. it isn't efficient pulling in basement air instead of cold air from the living space..


All this really sucks to try to do.. I was severely hurt in an accident two years ago and ended up semi-parlyzed in my leg.. so... I have been using friends to do most of the physical stuff.. I'm lucky to have good friends.. that's for sure!


I'll let you know how things go today.. I REALLY appreciate all your advice and help on this.. I'm a double master ASE tech (auto & heavy truck/diesel) so this is similar in diagnosis.. but.. I have no service manuals or anything.. so.. your experience and information is SO HELPFULL! I accidentally clicked on "accept answer" yesterday and I hope that didn't screw up what you get.. let me know if it did..ok?

no it did not mess anything up by clicking accept. I am glad I can help. just let me know if and when I can be of further assistance. Pleasure working with you. Not every day we get to work with someone that is "Hands On". Thanks again! servtech50

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