furnace will not shut down
First double and triple check the motor wiring to make sure everything is correct. It is possible you may have unknowingly bypassed a switch or control wire.
Next, make sure that the limit switch is connected and working properly. This turns off the furnace when the proper room temperature has been achieved.
In my Rheem RGAA furnace, this switch is mounted inside the furnace housing but outside the plenum, about one foot above the fan motor. Make sure it is still connected in circuit. In my furnace, one wire from this switch goes to the 24volt gas valve and the other wire goes to the R8239A transformer/relay module. Once you confirm that the limit switch is still connected in circuit, remove the cover of the limit switch and watch the internal round dial. I have an a.c. power switch mounted on the outside of my furnace housing. I would turn that off to allow the furnace to cool down. You will see the limit switch round dial rotate in one direction. Then turn it back on. As the main burners heat the air, the limit switch round dial will physically rotate in the opposite direction until a certain temperature is reached before turning on the fan motor. This will confirm if the limit switch is working or not.
Last edited by HoosierJayBee; 03-04-2010 at 07:52 PM.