Fix a Furnace Blower Fan Won't Turn On... Capacitor & Limit Switch

#furnace #troubleshooting #hvac My Goodman GMP-075 furnace would turn on when my thermostat called for heat, but the blower fan just hummed and wouldn't start, so we couldn't get heat blowing throughout our house, it would just warm up at the furnace, create a burning smell, and then go off because it wasn't getting any fan movement. In this video, I go over the problems that I had to troubleshoot to get the blower fan to start, to keep the furnace from tripping the limit switch, and what was wrong with the control board. See my further explanation of the limit switch repair in the description below. Contents of this Video: 00:00 -Explanation of malfunctioning fan blower 00:35 -Troubleshooting the furnace 00:49 -Capacitor (shiny thing on the top right) is bad 01:21 -Bad limit switch for heater (explanation on how to fix below in description) 02:34 -Fuse for control board was blown 03:11 -Change Filter, too! First off, here's what I ended up needing: Affordable Digital Multimeter: https://amzn.to/3r9izbr Dual Run Capacitor (check your faulty capacitor before purchasing): https://amzn.to/43kjpQ5 Filter (mine is 20x20x1): https://amzn.to/3PvgnoK 3 amp fuse: https://amzn.to/3PAMpiY (These affiliate links will take you to a product that, if you purchase it, will give me a small commission that helps me make more videos. Thanks!) I was starting to think my thermostat for my furnace wasn't working, but it turned out the capacitor was bad, but it also had some other problems. I had previous experience with run capacitors not working, and the hum of the fan told me this was probably part of the problem. I turned off the furnace, checked the capacitor and limit switch with a digital multimeter, and also checked the control board. This last part was from reading on several online forums about a similar problem with GMP-075 gas furnaces. On another note, the 20x20x1 filter was pretty filthy. We had smoke from forest fires here in the Northwest, and it was really black and gross. Best to change that out because it can affect the pressure switch in the furnace. If the filter is too clogged, it is dangerous for the furnace to keep recirculating the air through the house if it can't move freely through a dirty filter. LIMIT SWITCHES: The limit switch was tripped. I reset the limit switch by tapping on it on the ground (it actually works)-- and then check the continuity with a multimeter. Replaced all of those and it fired right up. So, here's the deal with limit switches. They are effectively a safety switch for a furnace or heating element, like in a dryer, so if it gets a short or goes WAY past the acceptable temperature, it has two different kinds of metal inside the switch. One of the metals reacts to heat differently than the other metal--and quicker. It will curl the metal upward, and away from the contacts that keep continuity for the circuit. It the metal gets too hot, this will cause the switch to break the circuit so electricity can't keep making the heater get hotter and hotter. On a lot of these switches, you can just pull it from the furnace, tap the flat side of the switch hard on the floor or a solid table, and it will often make that 2 metal plate go back down flat onto the contacts. This will re-establish continuity on your switch and electricity can once again flow. Now, don't just fix this switch without figuring out WHY it tripped--it's for your safety--so you don't burn down your house! In my case, the capacitor was bad on my blower fan, and it wouldn't turn on to blow air. This means the heater would get too hot without moving that hot air AWAY from the furnace! This is definitely not a step by step video for a full repair, but the capacitor and changing out the filter might do what you need.