Have HVAC Questions? Ask an HVAC Expert for Answers
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
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.
#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
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..
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?