Problem: I have the following problem, but only intermittently. It usually happens about every tenth time or so that the furnace goes off, but it has been happening less frequently lately. Not sure why.
I have a Carrier 58DH. The call for heat goes, the gas ignites, the unit heats up, but then the blower doesn’t engage. After a while, the safety switch kicks in and turns off the unit which is overheated. There is also a burn smell in the house. I wait for the unit to cool down, trip the reset button on the top of the blower, turn the furnace back on, and it generally operates well for a number of cycles.
Any idea what might be wrong? I had the control panel changed out on this unit about five years ago. I know it is an older unit (1984), but I can’t afford a new one at the moment.
Answer: The burn smell could either be caused by the heat exchanger getting real hot and burning the old dust off the heat exchanger or the blower motor could be getting too hot and causing an burning electrical smell. I would suggest that the next time the blower does not come on to turn the power off to the furnace, take the furnace door off and lightly feel (touch) the blower motor to see if it is hot or not. If the blower motor is hot I would see if you can spin the squirrel cage (blower wheel) freely. You should be able to spin the blower wheel and the wheel should continue to turn for a few seconds after you spin it. If the wheel does not turn freely then you probably need a new blower motor because the motor bearings might be dragging the motor down and causing it to over-heat. If the wheel turns freely, I will suggest having the motor run capacitor checked. Some appliance parts places will check capacitors out for free. We sell capacitors on the following page: Please click here if you are interested in seeing the capacitors we sell. If the capacitor checks out OK then you might have a control board problem. The fan relay on the control board could be acting up periodically and causing the fan to not turn on. If you want me to recommend a control board I will need your furnace’s product number. I hope you get the problem figured out. I also hope that you have a great day! Please email us anytime if you have a question. Our email address is: firstname.lastname@example.org We would love to help you out and earn your business!
Steve Arnold, https://arnoldservice.com