fan for the a/c & heater unit will not turn off


Old 12-31-00, 09:47 PM
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My a/c & heater unit is located in the attic. One day I
changed out the filter and replaced it with a new one. I put the cover back on and could not get the fan to cut back on. So I took the door off again and started looking around
and I noticed a switch of some kind in the top left hand corner so I pushed it and presto the fan cut on I put the
cover back on in a way that the top hinge of the door pushes
the switch but the fan runs non-stop. i have checked the
green wire to make sure that it is not touching any other wire. I have also changed out the thermostat. The house was
built in 1990. I have recently moved in. Please help
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Old 12-31-00, 10:26 PM
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Information is missing in your posting. <Retrace the events exactly as they happened> That switch you found is the door safety switch. It's there so the electrical system will totally shut down <nothing works> should the filter access door not be in place or in place incorrectly.

Pushing it in with the finger activated the fan but it shouldn't have, if the thermostat was set to the off position before you removed the filter access door. Which means the fan was running <the furnace was heating the house?> prior to your removing the door.

Removal of the filter access door panel, shuts off the electrical system when the safety button popped out, as it was designed to. Installing the door panel correctly, as you did the second time, reactivated the fan because something was already set to run. Possible the fan "ON" switch located on the thermostat?

The door safety switch will not activate the fan by itself. The door safety switch only interrupts the electric to the furnace in either the heating mode or the A/C mode. Neither heater nor A/C will work with the filter access panel removed.

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