When I viewed my furnace board terminal I found that the C terminal already had a wire going to it. This is on the back of the thermostat packet. Today I tried to turn on the AC through my thermostat and the fuse blew on my furnace. You just need to have a multimeter and check continuity between two contacts. Fuse blows. I bypassed the thermostat and the AC worked just fine. I was blowing the 5 Amp fuse on the control board for my forced air gas furnace. Ran on low heat and seemed to work for about a week (just luck for that week). When I attach it to the C terminal on circuit board, it blows the 5 amp onboard fuse. However, you need to make sure to get the same wattage ratings as before. This can spell major problems as the temperatures continue to dip lower and lower with each passing hour. I'm wondering if the thermister 8193776 or the high limit thermostat 66156 could be malfunctioning. Malfunctioning Thermostat Wire If your thermostat wire touches the metal frame of the furnace, this can cause a blown fuse. I tried several things but noted that the fuse blew even with the thermostat turned down (off). Michael Joseph has more than 20 years of hands-on experience as an avid home handyman and had 10 years in the construction industry, specifically in the field of HVAC. I have replaced the fuse and each time I engage the heat switch on the termostat, the fuse blows. I followed the directions and used an unused wire in my bundle as the C wire. This could be a complicated do-it-yourself fix and ⦠If you suspect that the fuse on your furnace has blown, here are the next steps that you need to take to remedy the situation. I've completely cleaned the machine including the blower - dismantling the machine to do so. You may suspect a blown fuse and wonder what you can do to replace it or prevent it from occurring again in the near future. If the thermostat is working and the circuit breaker hasn't tripped, the heater needs servicing. During those hot and muggy summer months, or during those subzero cold winter months, heat pumps can ensure room temperatures are comfortable for your entire family. You can quickly determine by checking resistance with a multimeter. This is where the fuse blew, in the airing cupboard. The fuse that keeps blowing is a thermal fuse and is caused by low air flow. When a thermostat wire touches the metal frame of the furnace, it can deliver more voltage than the wires are designed to handle. I replace, no problem for a while and then blow. Of course, you may have burnt out the blower motor which can also result in a blown fuse. Loose wires, in general, are often responsible for blown fuses. I am adding a WiFi thermostat. i replaced the controll board and it ran well for two months. First the thermostat needed batteries, then we were unable to get the unit to blow heat because of fuse blowing. The leading cause of thermal fuse burnout is obstructed airflow. We have been mostly using just the fan since the nights arent cool enough for the furnance. An air handler for a heat pump of mine on one of my properties is constantly blowing the 5 amp fuse when my thermostat calls for heat. All of these particles enter into the blower motor and cause the fuse to burn out. My furnace is a Concord model CG90UB. This particular thermal fuse is located on your dryerâs blower wheel. Page 1 of 2 - Fuse Blows On Thermostat - posted in Outback HVAC & Appliances: Camping for a month this summer and had the fuse blow on the thermostat. Some plastic fuses will have the same wire, but it is only visible when viewed from the side. Playing detective can be a little tricky, though. Type above and press Enter to search. I have R,W,G,Y wires. Yes... we are 20 years old. Once you know how to check your furnace fuse, you can replace it easily. My furnace is blowing it's low voltage fuse every cold morning during when the thermostat disables the setback and does the "smart warmup". Whenever I replace the fuse, I replace the companion high limit thermostat. The furnace requires a lot of electricity to run, and your home may not have the means to support it or there could be a short in the system. I can get the fuse to blow reliably if I have the thermostat call for aux heat. Took blown fuse apart to see how it works. I removed all the wires going to my thermostat and it would not blow the fuse when powered on. Plus 2 extra coming from upstairs that go between humidifier and humidistat. I took the 240V reading from the AC Live and Earth, while the old thermostat has power to it. From here, you can follow the instructions in your owner’s manual for how to replace the fuse. Anything else, let me know. It monitors the temperature of the dryer, and when that temperature gets too high, it shuts power off to the motor (not to the heating element !!!) �I haven�t failed. 4th fuse blew and now I can take my ⦠Perhaps the fuse that is installed in your furnace is not the correct wattage. Fuse blows. If the unit runs fine the thermostat ⦠So I ran an extra wire for the C wire. Try installing a fuse with a higher rated one to see if that will remedy your problem. Fuse blows. So it gets cold in the house and I realize I have not heat. Here are a few of the most common problems: This is one of the most common reasons why the furnace fuse is blown. Some fuses will have a glass display window with a metal bar running through. turn on the power, press in the door safety switch. If your heat pump is not blowing cool or warm air, or if it is not coming on, check the fuses and reset them, if necessary. If your furnace fuse blows when the heat turns on, you have a major problem on your hands. Normally when a fuse or RCD trips and the appliance is the issue it will be as a result of either a dead short or earth leakage and it will happen every time the product is switched on. You may also need to use your multimeter to check if your fuses are blown. Tip. The #1 question asked by NEW MEMBERS. Loose wires, in general, are often responsible for blown fuses. My best suggestion is to turn everything off at the breaker and use a volt meter to check for continuity between all the thermostat wires. Make sure that you thoroughly investigate all of the potential causes and seek professional help when necessary. As soon as you request heat the fuse blows and when I try to run the fan to on nothing happens. Jumper the R and the W on the circuit board for the t-stat. This can be the sign of an electrical problem, putting you at risk of a serious fire. Start by making sure that you turn off all electricity running to your unit. How many people are guilty of neglecting their air filters? I have a Carrier furance model number 58STA/STX and my LED is indicating a Secondary Voltage Fuse is Open. Our 20th year anniversary is May 21, 2020. It is a Potterton HE boiler, and a Honeywell controller. You need to find the root cause of the blown fuse on the furnace circuit board before you cause damage to the unit. Make sure you have a good fuse and then reattach them one at a time. I find it really unbelievable that install did not wrap wires with at least electrical tape ( now shrink tape is used) and zip tie wires together so this issue did not occur. Save my name, email, and website in this browser for the next time I comment. With a good fuse in the AC work fine and you can switch the fan from Auto to Fan on with no problem. I replace but have to squeeze the fuse holder because it was loose, I hit the board with the pair of pliers and blew the board. However, if your HVAC equipment has low voltage, it can cause the screen on your thermostat to go completely blank. 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