High limit switch open- but only faults in night and extreme cold
I have an Armstrong Air furnace that is not blowing hot air. Noticed
the LED light is flashing four times, which, according to the alarm
code means I have a high limit switch open. Turned the furnace off and
back on but that didn't do any good. Strange thing is, it only only faults in night and extreme cold. Already replaced air filter ans reset entire system. problem still persists.
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Re: high limit switch open- but only faults in night and...
Hello , I can try to help you out on this one , It sounds like what is happening is that your exhaust vented up is condensating from the heat in the pipe and the cool in the attic or wherever the exterior of the exhaust pipe travels. It is very common because your exhaust/flu pipe is not insulated.
To fix this issue you must drain the water/condensation from the small 5/16th hoses in front of the blower assembly , just pull them loose and angle them downward to drain. This should fix the problem if this is the problem.
Let me know how it turns out or if you have anymore questions. Phil
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Turn power off & on again. Watch to see if it cycles...it could be the hot surface igniter if you don't see it turn bright orange. If it goes straight to blowing cold air, then normally it is a limit switch open- mostly manual reset - thermal disc-located around flame rollout.
Hi, did he bypass the high limit to see if it was bad? Sounds like you are getting false codes and you have a problem in your module or main board, which ever you have. The way it is acting, saying the high limit is open but the tech says its not, I would change the board. Shastalaker7
Hello, this indicates a open limit switch. A limit l switch will open when the temp in the heat exchanger gets too high and this switch shuts the Furnace down for safety. Usuaully a dirty filter, weak blower motor, dirty blower wheel will cause a limit switch to open.
Hello, a limit switch will open when the furnace gets too hot, the switch senses that the temperature is too hot and shut down the furnace for safety. Uusally a limit switch will open because of lack of airflow across the heat exchanger, this could be due to a dirty air filter, dirty blower wheel, or the blower motor itself is not running at the proper speed. I hope this helps.
Code 33 is "limit is open or flame switch is open"
FIRST make sure the filter is clean. Turn off unit then turn back on.
if it works but then later gives you a 33 code then you might have a dirty a/c coil (if you have a/c) that will cause the limit to open. 1st try that
It means that the furnace isn't igniting and for safety the control board is preventing the gas valve from opening. Turn off the power to the furnace for a few seconds then observe what the furnace does in heat mode. Some furnaces will run the blower for a minute after you power it back up. After that see if the furnace tries to come on. If you are still getting the code then one of you high temp limit or roll out switches has tripped. Now is the time for a service tech. Make sure that you check you filter and air flow too. Low air flow means the furnace may be over heating. The other thing is the hot surface igniter. Look closely at it with the power off. Do you see a white spot on the element or a crack. If so the HSI is bad. It's an easy replacement but DO NOT touch the carbon element with your fingers and be very careful handling it as it is EXTREMELY fragile.
blowing cold air on this furnace usualy caused by high limit trip, or flame roll out. the first one, (high limit) is from insf. air flow. (blocked filter,bad zone damper?
The second,(flame roll out) caused by bad heat exchanger,blocked vent.ect.
If you know where the high limit switch is you can always cut the two wires and wire them together causing the limit to close. But what you have to watch out for is why the high limit is not closing. That means in your return air either you have a dirty return air duct, dirty filter, or you don't have all your registors open to allow the heat to escape the heat exchanger. Just watch over riding the system. The high limit switch should either be on or behind the blower, in the middle of the system right under the heat exchanger. any other questions about hvac just ask.