I have a Ruud 90 Achiever, model number RCBA-3765GG17XI, MFD: 2003 using natural gas in my condo. Last week I noticed that the blower was turning on but no heat was coming out. I tried to turning the thermostat to the "off" position and then back to "on". When I did this the pilot would click and the burners would ignite for about 3 seconds and then turn off. After that I took both of the front panels off the unit and nothing looked wrong so I put the panels back. When I did this the blower immediately started and the burners lit and stayed on. My heat was working fine until today. I just repeated taking the doors off and replacing them with the same results. Does anyone know why this is happening?

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Originally Posted by johnlynch23

I have a Ruud 90 Achiever, model number RCBA-3765GG17XI, MFD: 2003 using natural gas in my condo. Last week I noticed that the blower was turning on but no heat was coming out. I tried to turning the thermostat to the "off" position and then back to "on". When I did this the pilot would click and the burners would ignite for about 3 seconds and then turn off. After that I took both of the front panels off of the unit and nothing looked wrong so I put the panels back. When I did this the blower immediately started and the burners lit and stayed on. My heat was working fine until today. I just repeated taking the doors off and replacing them with the same results. Does anyone know why this is happening?

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Clean this part. Flame sensor. Easy does it near the ignitor they are sensitive.

Hvac just gave you your fix. If you have questions about locating the flame senser, just ask. 99 percent sure that flame senser is your problem. A ruud as new as yours will have the flame senser located at opposite end of burner as ignitoin.