Question: Hi, I have a BDP/Carrier furnace from 1987. The burners will light and run for about a minute or two, but within a minute after the blower turns on the burners and the pilot go out. If I remove the cover to the blowers the burners will stay on and heat the house. I checked to make sure the air intake vents in the house are not covered. Any suggestions?
Answer: Hi Darren! Great question! This sounds like the furnace is probably over-heating and going off on the limit. I would suggest that the next time the furnace gas goes off prematurely that you check the limit with a voltmeter to see if the limit is the problem. You might need a new limit or more than likely the limit is doing its job by cutting off the furnace to keep the furnace from getting too hot. Over-heating of the furnace can be caused by as you have already checked some of the registers being blocked or turned off. Overheating of the furnace can also be caused by a dirty filter, dirty blower wheel, slow blower motor, (might need a new capacitor) stopped up or blocked air conditioner evaporator coil, or the gas valve gas pressure being set too high. I would suggest checking the easy causes first like the filter, dirty blower wheel, or have the capacitor on the blower motor checked. We have two really good YouTube videos by AC Service tech below that show the different types of furnace limit switches and how to troubleshoot limits. Thanks so much to AC Service Tech LLC for making this video! Best of luck in finding and fixing this problem.
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