I recently replaced my fan limit switch when I noticed that the blower fan would not turn on and the unit would shut off on high limit. There was no change when I put in the new switch. After about 5 minutes the blower fan turns on and shortly after the induction fan turns on and then the furnace ignites. What should I look at to find the root cause of the problem. Thanks in advance for your help.
This thing is just a switch. Instead of you making or breaking the contacts with your fingers, as you would on a light switch by flipping the switch up or down, this switch makes or breaks the contacts based on temperature, so troubleshoot this switch just like any other switch. This was a very good informative video on the description and operation of this switch. Unfortunately, they didn't cover how to troubleshoot this switch, but I'm sure they didn't because they wanted to keep the video short as possible. I'm pretty sure they covered it in the presentation at seminar. I honestly don't think both the old and new switches are bad. It's possible but very unlikely, so I think you should first check the power coming into the switch. Power should always be at the switch during normal operation. Take the cover of the switch and check for power coming in with a voltmeter set to AC volts. You should have 120V on the "fan" side of the switch, You already know the "limit" side of the switch works so you don't have to check that. Once you confirm you have power coming into the switch, you can now troubleshoot the switch for proper operation. Watch this video on how to check the switch with an ohmmeter for proper operation. Before you start, turn all power off to the furnace, and confirm power is off by checking with a voltmeter. After confirming power is off, disconnect both wires from the fan side of the switch and do what's shown on this video. If you don't have experience working with electricity and a multimeter or don't feel comfortable doing it, then I highly recommend hiring a professional to do it. It's not worth getting seriously injured or ending your life just to save a few bucks. ruclips.net/video/Pyz9MxgHn5k/видео.htmlsi=9S3bgvMi93t1t8oh This other video also shows you how to troubleshoot this switch ruclips.net/video/PFN_vZqXXR4/видео.htmlsi=EQ1vWAL__QjAK_4N. Watch both videos to get a better understanding of the troubleshooting process.
This is the most informative step by step video on this subject. Just what I was looking for! Thanks
Glad it was helpful!
Good knowledgeable information
I recently replaced my fan limit switch when I noticed that the blower fan would not turn on and the unit would shut off on high limit. There was no change when I put in the new switch. After about 5 minutes the blower fan turns on and shortly after the induction fan turns on and then the furnace ignites. What should I look at to find the root cause of the problem. Thanks in advance for your help.
This thing is just a switch. Instead of you making or breaking the contacts with your fingers, as you would on a light switch by flipping the switch up or down, this switch makes or breaks the contacts based on temperature, so troubleshoot this switch just like any other switch. This was a very good informative video on the description and operation of this switch. Unfortunately, they didn't cover how to troubleshoot this switch, but I'm sure they didn't because they wanted to keep the video short as possible. I'm pretty sure they covered it in the presentation at seminar.
I honestly don't think both the old and new switches are bad. It's possible but very unlikely, so I think you should first check the power coming into the switch. Power should always be at the switch during normal operation. Take the cover of the switch and check for power coming in with a voltmeter set to AC volts. You should have 120V on the "fan" side of the switch, You already know the "limit" side of the switch works so you don't have to check that. Once you confirm you have power coming into the switch, you can now troubleshoot the switch for proper operation. Watch this video on how to check the switch with an ohmmeter for proper operation. Before you start, turn all power off to the furnace, and confirm power is off by checking with a voltmeter. After confirming power is off, disconnect both wires from the fan side of the switch and do what's shown on this video. If you don't have experience working with electricity and a multimeter or don't feel comfortable doing it, then I highly recommend hiring a professional to do it. It's not worth getting seriously injured or ending your life just to save a few bucks. ruclips.net/video/Pyz9MxgHn5k/видео.htmlsi=9S3bgvMi93t1t8oh
This other video also shows you how to troubleshoot this switch ruclips.net/video/PFN_vZqXXR4/видео.htmlsi=EQ1vWAL__QjAK_4N. Watch both videos to get a better understanding of the troubleshooting process.