I suspected this issue during the winter and confirmed it now in the summer. Regardless of the temp in my home, the blower motor runs non-stop.In the winter this must have been causing my home to got through a permanent heat/cool cycle as the blower would bring cool air in after the home was at the right temp. Then the temp would get low, the furnace would kick in to heat the home and on and on.In the summer now it seems to be doing the same thing but with the A/C. Once the home is cool enough, the blower keeps bringing in outside air with the A/C off now. This causes the home to heat up and on and on.

Jan 16, 2012  How do I reset my limit rollout switch on my Carrier Heate - Answered by a verified HVAC Technician We use cookies to give you the best possible experience on our website. By continuing to use this site you consent to the use of cookies on your device as described in our cookie policy unless you have disabled them. The blower will continue to run until either the system is reset, or the limit switch closes. I believe high limit switches are normally closed,.

The adverse effect at night is it's making my home too cold since the outside air is already quite cool.I check this question.I can manually turn off the limit switch and the blower stops.How can I test whether the problem is the limit switch or the thermostat? If the high limit switch was bad, the furnace should not fire. When the high limit switch trips, the flame/heating element will be shut off and the blower will continue to run to clear the heat. The blower will continue to run until either the system is reset, or the limit switch closes.I believe high limit switches are normally closed, and they should always fail open. Which means when they go bad, or the temperature gets too high they open the circuit. To test a limit switch, you'll want to check continuity to determine what state the switch is in.

If there is a serviceman switch, turn it off. If not, shut the power off at the breaker panel. Open the access panel and locate the high limit switch. It should be somewhere on the hot box. Disconnect the wires from the switch (don't forget which goes where).

Download free serial number of idm. Using a multimeter, test for continuity between the leads on the switch.There is an easier test to check limit switches, but it should only be performed by HVAC techs. So I will not discuss it here.If the circuit is open, you'll want to replace the limit switch.If the limit switch is adjustable, make sure it is set properly according to the manufactures specifications.If the limit switch tests OK; or you've replaced it and still have the issue, you'll want to focus on the thermostat.From your description, it sounds more like a problem with the thermostat. Most safety mechanisms in furnaces do not let the furnace fire if there's a fault, so if you're getting flame I would not suspect a limit switch. I would suspect either the thermostat has gone bad, or it is miswired. If the fan is always on I would suspect either the fan switch has failed closed (is always in the ON position), or the fan wire was incorrectly bonded to the voltage feed line.Thermostats are basically switch boxes. They'll have one live wire R (usually 24v in the US, or line voltage in other parts of the world), one heat call wire W, one blower fan call wire G, and optionally a cool call Y, and/or.

When the thermostat wants to warm up, it will connect the R to W and G which tells the furnace the thermostat is cold and needs heat. If it's hot it connects the R to Y and G, to tell the furnace it's hot and wants to be cooled down. If you have a FAN control and you turn it to ON, the thermostat connects R to G and the blower fan turns on.The easiest way to rule out the thermostat, is to replace it. Troubleshooting thermostats is a pain in the ass, so it's much easier to simply switch it out.If you've changed the thermostat and you're still having the problem, call an HVAC tech. I have an older furnace that uses the fan/limit dial type device and had the same problem running in heat mode. The burners would cut off at the desired temperature in the house but the blower would run continuously, blowing cold air in the house.I raised the thermostat setting higher than the house temperature to check if the gas burners would turn on while the fan was running. By the burners coming on, that let me know the limit side was alright.

I then thought the fan side must be stuck on. I turned the power off to the furnace and tapped the fan/limit device a few times with the handle end of a screw driver to see if it would jar it loose. I Turned the power on and that solved the problem.This doesn't mean it won't happen again, but I haven't had any more problems. This is a quick diagnosis before having to test with a meter.

My wife noticed it first one evening and it was fixed ten minutes later. First problem with the device in 28 years. Most likely a sign it's time to replace.

Not hooked up to an AC unit.

Project:Fixing the #13 and #33 error on a 90% efficiency carrier furnace with variable speed blower motorDifficulty Level (Easy, Medium, Hard, Insane):EasyProcess:Two nights ago before going to bed I noticed that the house seemed colder than normal so I checked out the thermostat and saw that there was a 'System Malfunction' notice. I decided to go down to the furnace room and have a look at it.I had a slight suspicion as to what the issue could be and just like I expected I saw the #13 error.

After consulting the error code section in the manual that came with the furnace it specified a 'Limit circuit lockout' error.The reason I was expecting this error was that two days ago I got the #33 error (Limit circuit fault).Basically what that means is that one of the thermal cut-off (TCO) switches would trip and throw the #33 error, but this time it seems like the TCO/Limit switch failed and got stuck in the open position.As it was getting late, I decided to turn off the furnace main switch and see if it would reset over night. Unfortunately, at 6:20am when the house should be warming up it wasn't so I knew I'd have to do some more trouble shooting and then fix the issue.I hauled out the volt meter and confirmed that the limit switch was in fact showing no continuity and had failed in the open position.I disconnected the two wires and temporarily by-passed the limit switch and spent the next hour sitting beside the furnace while the house was heating up to a nice temperature. Of course, I couldn't leave the furnace on without the safety feature of the limit switch but with my stay at home wife and three small kids I wanted to make sure the house was at least not cold.After some more research I concluded that the two most likely causes for the error were:1.

Stuck high-heat gas valve2. Broken limit switchI suspected #2 because admittedly, I had not been very diligent in cleaning out my furnace air filter, which I supposed caused a reduced air flow through the heat exchanger and consequently a reduced transfer of heat away from the furnace which resulted in the tripping of the limit switch.After sourcing a part through one of our local furnace repair shop I loosened the two screws, pulled out the old limit switch, put in the new one and everything was back to normal.Luckily, it was just a $30 part and since I did my own labor it was a fairly cheap problem. However, if I had to get a furnace specialist to come in, trouble shoot the issue, order the replacement part and come back to install it I would have looked at a bill of at least $300 bucks.Videos.

Manual override of the limit switch - NOT RECOMMENDEDLimit switch modelCarrier furnace typeThe replacement limit switchBrand new limit switchClose-up of the limit switchWhile I was at it I also cleaned the stainless steel probeTemperature right by the limit switch. Clearly after cleaning the air filter it was within proper limitsTools:Socket setScrew driverPliersThermometerVolt meterFlashlightMaterials:1 limit switchCost:$35.00Time:1hrSavings:$270.00Conclusion:House is nice and warm and no more errors.