My blower fan cycles on/off.


Old 09-09-20, 02:15 PM
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Join Date: Jun 2007
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My blower fan cycles on/off.

With the thermostat 'Fan' switch in the 'On' position, and the 'System' switch in the 'Off' position, (so both heating and cooling are turned off), the blower fan runs continuously as intended. However, after an hour or two of continuous running; the blower fan starts to cycle
on/off/on/off... It turns on for a few seconds and then turns off for a few seconds and repeats.

I've attached pics of the wiring diagram and the control board.

So far I've down the following to no avail:
o Replaced the filter.
o Removed dust from the inside of the blower fan.
o Removed the thermostat and jumpered R and G.
o Checked all the exhaust vents in the house.

Any advice would be greatly appreciated.

My control board cover.

My blower fan wiring diagram.
Old 09-12-20, 12:21 PM
Geochurchi's Avatar
Join Date: Nov 2012
Location: United States
Posts: 4,963
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Hi, can you access the blower motor? when it starts cycling can you feel the motor and see if it is really hot. shut the power off before putting your hands in there.

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