"stoneattic" wrote in message
...
Does anyone have an idea as to why the fan on my heater/AC would run
constantly when the thermostat is set to have the fan in "Auto" mode
but not run at all when in "On" mode?

The whole story:

My fan was running all the time regardless of thermostat setting,
including heat and AC off. I disconnected the green wire from the
thermostat and it kept running. From everything I read that indicated
a stuck fan relay. When I looked at the fan really it was cooked,
burned plastic, etc. So I replaced it with the same model. I'm
pretty sure I wired it exactly the same, I took notes, etc. So now I
got the weird situation described above. I picked up a new thermostat
thinking that maybe the burned relay took out the thermostat but it
does the same thing. That makes me believe I did screw up the wiring
but after much reading and checking and rechecking the wiring looks
right. Does any know what could cause this?

thanks

Depending upon the make and model of the unit, something other than the
thermostat is sending power to the fan relay. Some units use a delay timer,
which could be faulty, or shunted wires at the blower could cause it