This is the power coming right off the low voltage transformer. You should have a constant 24 to 28 volts AC between the R (red) and C (com) terminals on the control board no matter how the thermostat is set. We sell some transformers on the following page: Please click here if you are interested in seeing the transformers we sell. If the fuse does not fix the problem with the low voltage then you may have burnt out the transformer. You will probably need to replace your thermostat wire if you find it has shorted the fuse out. Most of the time I find that the animals have chewed through the thermostat wires and shorted them out or the thermostat wires over time have been pinched around the body of the furnace or air handler which has caused them to short out. If the fuse on the control board is blown this usually means that you have a short in the low voltage circuit of the furnace. You would be surprised how many people go without heat or cooling for hours and days and all the problem they have is the switch on the side of the furnace is not turned on or the blower door is loose after they change a filter! I try to go over this with my customers before I make a service call. Most of the time you can get these fuses at a local hardware store. We have a picture of a fuse on the control board below.
If you aren’t getting any voltage then you might have a bad thermostat, bad thermostat wiring, not getting 110 volts to the furnace (make sure switch on furnace is flipped on and blower door safety switch is pushed in) or a blown fuse on the control board. If you are getting 24 to 28 volts between the W and C terminals then your thermostat and thermostat wiring are in good shape and doing what they are supposed to be doing. Us a volt meter set to “Volts AC” and test between terminals W (usually white wire) and C (Com) and see if you are getting 24 to 28 volts between these two terminals. Tape the blower door safety switch shut (if equipped) and set your thermostat so it is calling for heat. If the draft inducer does not start then you probably either have a thermostat, thermostat wiring problem, electrical problem, control board problem or a bad draft inducer.Ģ. The first thing that is supposed to start when a furnace starts up is the draft inducer.
Inducer Motor Turning On and Off Thanks so very much to Word of Advice TV for making this excellent troubleshooting video!ġ. Here is a little summary of what is covered in the video: 1. Is your inducer motor not turning on? Or perhaps the inducer motor is noisy or stuck? Does not shut off or turns on and off? All of these question are covered in this video along with inducer motor troubleshooting, testing, and checking. We have another really good YouTube Video made by Word of Advice TV which covers the following information: Thanks to acservicetech for making this great video! This excellent video was made by acservicetech.
We have two really good Youtube videos below that show the 8 top problems when a furnace draft inducer will not start. First, and most important things to remember is turn your electrical power off to the furnace. I always troubleshoot and test the least expensive parts first, such as the thermostat, pressure switch, limit switch and rollout switches to make sure they are all closed and operating correctly before I go to the control board. Solution: Any combination of the above problem or problems could be caused by a bad furnace control board or bad draft inducer. I think my furnace’s draft inducer is having problems?įYI: *You would be surprised how many people go without heat or cooling for hours/days and all the problem they have is the switch on the side of the furnace is not turned on or the blower door is loose after they change a filter! One customer blamed his cat for turning it off! LOL! I try to go over this with my customers before I make a service call so I do not waste their money. Problem: Draft inducer will not start, ignitor will not glow or gas valve will not open.