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I have a Concord 80 Plus Gas Furnace. I am starting the furnace for the winter and it gives me a LED code of open limit switch or limit switch circuit. Everything seems to work fine up until the point where the blower needs to turn on. I had the same problem last year but got a tech to fix it. I am not sure what he did. Any response would be truly appreciated
Likely he replaced the limit switch. If you can find the receipt from last year, it may tell, maybe even have a part number. It sounds like something is wrong if it needs a new limit switch again or cleaned. Maybe you need a real tech to adjust the air to gas ratio or something.
Thanks for the response but he did not replace anything. I know that for a fact. From what I remember he told me that it was the gas control switch. Supposedly that is what it was. I wasn't there when he got it running right. He told me this afterwards. Well I know I did the same thing last year as I did this year and it is doing the same thing. I know that the gas control switch is on because the burners light up.
If the limit switch is dirty, where is it located and can I clean it? This house was built in 2004 so the furnace is not old.
It sounds like a main limit as Labman pointed out. Limits can become fatigued if they open and close to many times. The tech may have just reset it by tapping on it, if so, the part should have been replaced. Be sure after the limit is replaced you have good airflow and check the temperature rise. Supply air temp' minus return air temp' should be aprox 35-55 degrees on an 80% furnace. The temp rise should be on the nomenclature panel inside the furnace burner compartment. Be sure filters are changed often and all your registers are open and unobstructed.
What does the switch look like and where would it be located? Thanks againQuote:
Originally Posted by labman
Limit switches used to be short and squat. I think newer ones may be longer and narrower. They are located on the heat exchanger, the tubes the gas flames heat. Should have 2 wires running to the circuit board.
Has anyone answered your question?Quote:
Originally Posted by toro5702
I believe I found the limit switch. It's a round thing with 2 violet wires and a small hose. How would you go about testing it to see if it works? I can I just connect the 2 violet wires directly while the heater is running to see if the blower turns on?Quote:
Originally Posted by labman
No not yet.Quote:
Originally Posted by efr4
Hose? Sounds maybe more like a pressure switch to signal the inducer is on. Perhaps look some more.
The main limit is mounted to the center of the back wall above or below the burners (depending if it's an up or downflow model.) It is a board usually about 2" x 1 1/4" with 2 wires going to it. It will have a part number and temperature rating on it.
I believe I found it. I have a few questions though. Looking at the schematics it says it's the roll-out switch. Is it the same? If so, more or less how much does this part cost? And where can I buy it?Quote:
Originally Posted by NorthernHeat
My guess is $10 or less. If it is a generic switch, a HVAC supply should have it. Otherwise, you may need to see your Concord dealer.
I got the same problem but on one of them the inducer runs and it won't light and it doesn't send voltage to the igniter. On the other one it says something about a pressure switch it gives a code of 2 flashes and nothing runs on this one
Northern Heat, your awesome. Helped me out with my furnace in the cold of the night. Thanks
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