How To Test and Bypass The Upper Limit Switch On Your Furnace

in this video i'm going to show you how to check the upper limit switch in your furnace and if it is bad how to jump the wires so that you can get your furnace fired back up again now these upper limit switches i'll show you this is a upper limit switch for a train they usually go out when it's super super cold outside and your furnace is running at the higher limit now this one here is specified for 150 degrees to 180 degrees now a lot of times when it's super cold outside you're running at a higher limit and you have a clogged air filter you're going to burn one of these up so you go down check out your furnace it's blowing and it's running but it's not blowing hot air i'll show you how to test it and most often than not you can't just go to a hardware store or call somebody up and get one of those upper limit switches you either have to do a service call which is probably going to cost you about 160 200 or you can buy one off amazon for about 40 bucks i have it shipped the next day and while you have this jumped your furnace is still running it's just not something you can quickly get so i'll show you how to run a jumper wire to keep your house warm if this ever goes out now if you don't have a volt meter and if you look through the sight glass of your furnace you'll see that red indicator light flashing and it's usually going to flash a certain a number of times and then you need to pull off your panel and look at the diagnostic code well there's going to be a diagnostic schematic in your furnace somewhere it might be on the inside or in this case it's on the back of the lower panel and you look over here under diagnostic codes and you'll see right there where it says four flashes open limit switch that's how you can tell if you have a faulty upper limit switch if you don't have a volt meter so another way to check is to use a voltmeter here's the upper limit switch i pulled out as you can tell it's pretty burned up and it's warped set your volt meter on ohms take your two probes and touch these two contacts and if it's good it will say zero any other reading then it means this upper limit switch is bad so right there is the upper limit switch and we're going to pull those two wires off and jump the wires just make sure your furnace is totally shut off you're just going to pull the wire straight off depending on where your upper limit switch is in your furnace uh it's kind of hard to get fingers back in here so i'll use these pliers and now to jump those wires make sure you use a piece of shielded wire i saw in a couple videos people actually used a paper clip absolutely do not use a paper clip you want to make sure that the wire you use is completely shielded so it doesn't touch any ground in the furnace and now you can go ahead install your lower cover give the power back to your furnace and it should fire right up now you gotta remember you bypassed a upper limit safety switch so this could actually put out some super hot air now in order to kind of monitor it i stick a meat thermometer in one of your supplies or maybe in a kitchen a bathroom wherever and monitor the temperature of the air coming out of your supply or your kind of baseboard vent it should not be over 120 degrees if it is you'll have to turn your furnace off let it cool down a little bit and then you can turn it back on again but that's one negative on bypassing that upper limit switch as it doesn't have that cut off when it reaches a certain temperature hope this video was helpful and informational to you and thanks for watching

Channel: ADD is multitasking

Views: 78,623

Keywords: trane furnace troubleshooting, trane furnace blowing cold air, trane furnace continuous flashing red light, trane furnace not igniting, trane furnace not blowing hot air, trane furnace reset button, trane furnace 4 red blinking lights, high limit switch, how to jump a high limit switch, how to get your furnance running, bryant furnace troubleshooting, bryant furnace filter replacement, bryant furnace code 33, bryant furnace not igniting

Id: 5IULCDt2y_s

Length: 3min 59sec (239 seconds)

Published: Thu Mar 04 2021