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Old 04-08-2010, 10:54 AM   #1
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AC blower fan cycle on and off


I just started using my AC this year, I realized the blower fan cycle on and off. During the cooling cycle, outside unit will run continuously, but the blower will cycle on and off (random length).

I also observed that this only happened when indoor temp is high (above 75), if I the indoor temp is around 70, this problem goes away. Which makes me think the fan think it is over heating and shut off to protect itself and come back on when cool down some what.

Any idea which part is wrong, any sensor I need to replace?

Thanks.

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Old 04-08-2010, 11:59 AM   #2
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AC blower fan cycle on and off


You can spin the blower by hand and see if it's siezed. Verify amperage and test the capacitor. You probably need a new motor and capacitor.





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Last edited by beenthere; 04-08-2010 at 03:58 PM. Reason: Removed link to another forum
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Old 04-08-2010, 12:06 PM   #3
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AC blower fan cycle on and off


Thanks for your reply, it is not siezed, it spin freely, I can also feel lots of air coming out of vents when running. How do I verify amperage and test the capacitor?





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Originally Posted by Tech X View Post
You can spin the blower by hand and see if it's siezed. Verify amperage and test the capacitor. You probably need a new motor and capacitor.
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Old 04-08-2010, 12:20 PM   #4
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AC blower fan cycle on and off


Use a clamp on meter to measure the amperage on the cooling wire, which is usually black. Usually 7 amps or less is okay. Check the rating plate for amperage rating. Use a multimeter with micro farrad setting to test the capacitor. Remove the 2 wires from the capacitor and measure accross both terminals. The capacitor should have a rating printed on it. Usually 5, 7.5 or 10uf.

Try turning the thermostat to fan ON, without running the ac. Does the fan still cut out?




Last edited by beenthere; 04-08-2010 at 03:57 PM. Reason: Removed link to another forum
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Old 04-08-2010, 12:47 PM   #5
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AC blower fan cycle on and off


Use a clamp on meter to measure the amperage on the cooling wire, which is usually black. Usually 7 amps or less is okay. Check the rating plate for amperage rating. Use a multimeter with micro farrad setting to test the capacitor. Remove the 2 wires from the capacitor and measure accross both terminals. The capacitor should have a rating printed on it. Usually 5, 7.5 or 10uf.

Try turning the thermostat to fan ON, without running the ac. Does the fan still cut out? YES if room temp is high, in winter time (room temp below 70, it is fine and can run hours without stop)



Thank you again.
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