I have a Trane central heating a/c unit (about 20 yrs. old). With the fan switch on AUTO the blower works normally in the a/c mode. In the heater mode, the burners fire but the fan does not come on. The fan operates with the heater on if I manually move the switch to the ON position. So I can assume that the motor/connections are okay. My suspicion is that the heat activated relay switch has gone bad. Question: If it is the replacement of a relay and/or heat probe, is this a DIY job or do I need to call a technician? Given a decent manual, I think I can do it (if that's all it is). What would be a good source for obtaining service manuals for specific models? Thanks, Tobor

There is a weird phenomenom with my gas furnace. It seems to only happen when the temperature is too low. At night I adjust my thermostat to drop the temperature down to about 20 degrees, but when I do this, at some point of the night I can hear a fan come on in the furnace and cycle on and off for about 10 minutes. This will eventually stop and the furnace will eventually work properly and blow hot air and it even seems to be keeping the predetermined temperature fairly well. The only problem is with this fan (an exhaust fan I think) that keeps coming on. My fear is that it's going to break down by cycling like this. Also, one other thing I noticed, when I took off the front cover to look around, I noticed that the ignitor wire is right in front of one of the gas pipes where the flame comes out. That wire is being subject to some pretty hot temps. Is that normal? I figured it should be out of the way ingniting a pilot rather than the actual burner. And one las thing, one of the pipes/burners seems to have some metal deflecting the flame from shooting completley inside the interior pipe. Some of the flame is instead being directed upwards onto a metal (heat shield?). My first question, is the most pressing, but I thought I'd provide more info, as these may be related. David