Lennox G24M3-75A intermittent problem

______________________________________________________________________ My Lennox Gas heater G24M3-75-A2 was installed in 1999. WOrked fine till this year. The SUrelite Board (Lennox part 2418501) shows this diagnostic code Led #1 OFF Led #2 Slow blink The thermostat calls for heat and sometimes it will not fire just the exhaust fan runs continually. The following actions were performed by a qualified HVAC tech. Replaced the pressure switch (worked fine for 5 months) Same problem as before Replaced the exhaust fan motor (no change in symptoms). Viusally checked the exhaust vent for any problems. It was clear. Checked the condensation line off the pressure switch it was clear. Replaced the intake filters with new 3 M pleated filters The problem still exists with no change in symptoms. Any ideas would be appreciated. Jerry B Replies: Service Manager “Re(1):Lennox G24M3-75A intermittent problem” , posted Mon 29 Jan 11:50 ______________________________________________________________________ I would have him check these if he hasent already: – Check the pressure switch line (rubber hose) for cracks etc and make sure there are no leaks in it. – Check the voltage to the induced draft motor (it could be low causing the motor to run at a lower RPM) – Check the pressure drop across the pressure switch to see if it is a pressure problem or a problem with the switch again. He can check this with a manometer. TKG26 “Re(2):Lennox G24M3-75A intermittent problem” , posted Mon 29 Jan 20:11 ______________________________________________________________________ Its intresting how the tech first replaced the air switch and then later the ventor motor. Was the original painted black?(motor and housing?) For years now when u get that code and find a black ventor housing the repair is to order the new unpainted motor that includes a new un contaminated pressure switch.. Perhaps and its a long shot, perhaps they replaced the pressure switch leaving the old painted ventor on, wich continued to flake paint and contaminate the internals of the pressure switch with moisture and paint flakes and when they changed to the new version of the ventor the damage was already done to the the new pressure switch. Aside from that.. Is your chimney lined? Or B-vent. If lined with flex liner has it been inspected right at the base of the chimney? SIGNATURE “Always have a licensed HVAC technician perform repairs on your equipments. HVAC is not a do-it-your-self home project.”