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Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3971
Experience:  Experienced in all aspects of HVAC, both residential and commercial.
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I have a problem with my Lennox model c33-36b-2f-2. Heater

Customer Question

I have a problem with my Lennox model c33-36b-2f-2. Heater turns on but blower is not engaging. A single diagnostic LED light flashes 4 times. Opened the panel and error code is "open primary or auxiliary limit".
I have toggled the breaker to the unit. Issue persists.
I have replaced the filter.
Air intake registers are both clear.
It's 55 degrees in my house and 25 degrees outside.
Any ideas on how to resolve this?
Submitted: 10 months ago.
Category: HVAC
Expert:  Tim H. replied 10 months ago.

Hi, I'm Tim and I'm an HVAC expert here to assist you with your questions. Please provide all information I request as it makes it more difficult to troubleshoot something when I'm not there onsite. Essentially, you become my eyes and ears. Thanks for the opportunity to help. At the end of our dialog, you will have a chance to rate my service, but please wait until we are finished and you're satisfied you have all the information you need.

Is blower running and moving air through the house?

Customer: replied 10 months ago.
It is not.
Expert:  Tim H. replied 10 months ago.

Go to your thermostat and put fan switch on ON instead of auto. Make sure blower door is on tight. Any air movement?

Customer: replied 10 months ago.
No movement, blower not engaging.
Expert:  Tim H. replied 10 months ago.

Open blower door, reach in and see if blower wheel spins freely.

Customer: replied 10 months ago.
Confirmed it does.
Expert:  Tim H. replied 10 months ago.

You probably have a bad blower motor. This can be confirmed with a voltage reading at board.

Customer: replied 10 months ago.
Ok. Thanks.
Expert:  Tim H. replied 10 months ago.

If you have 120 volts to blower motor but it doesn't spin, replace motor. If no voltage, replace board.

Expert:  Tim H. replied 10 months ago.

It's got to be one or the other. That is why you are getting limit fault code. Furnace got so hot it tripped out on high limit.

Expert:  Tim H. replied 10 months ago.

Let me know if you have additional questions on this. Otherwise, good luck! Thanks for using Just Answer and please don't forget to rate my service as that's how experts get paid (thanks in advance for any bonus left). Otherwise experts work at their own time and expense. Feel free to post back with any additional questions.