[COLOR=#000000][FONT=verdana]hey I have a Lennox furnace, that the inducer motor will come on and spin for like 2 or 3 seconds and then shuts off. it will come back on after a few minutes and do the same thing again.I check the pressure, it is kicking in the pressure switch. on the schematic it shows a limit switch after the pressure sensor, if I take the wire off of that pressure sensor the indoor blower motor starts to turn instantly. in about 1 minute the inducer motor will spend and the furnace fires like normalit will run for about 10 or 15 minutes and then shut down. when it starts up it may or may not fire, if it does the burners will come on for about 1 minute and just before the blow motor comes on the burners go out. if I pull that wire off of that limit switch again it starts all over but never runs more than 15 minutes or so. I am NOT leaving that wire off I just momentarily take it off and put it back on when the blower motor starts. [/FONT][/COLOR][COLOR=#000000][FONT=verdana]I checked the error lights and they are blinking error code "Primary or Secondary limit open" . So I shorted all switches, one at a time to find the bad switch. gave same error on all until I shorted them all at once. I inserted a temp probe to make sure it didnt get sky high.The temps did get up to 150 degrees then gave another error code that says "Improper main ground or line voltage below 75 volts; OR: Broken ignitor; OR:Open ignitor circuit."[/FONT][/COLOR] [COLOR=#000000][FONT=verdana]I checked the voltage and the ground. I'm not sure about the broken ignitor because it did ignite for 45 sec. any clues? [/FONT][/COLOR]

For about a year our XE78 has had problems staying lit. A couple of months ago I took the flame sensor out, it appeared practically new. Gave it a cleaning anyway and popped it back in. The High Limit sensors were somewhat corroded, cleaned them up to. Everything else seemed in order. No loose connections etc.. Worked like a champ, until now. Now here's the run down. -Slow Flash = Normal No Call for Heat Turn on the thermostat -Flashing Fast = Normal Call for Heat Ignitor glows, jets kick on for roughly 5 seconds then shut down. a second after that.. -Continuous On = Replace Control Possible flame sensor?