Air handler blower only comes on in emergency heat mode

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  #1  
Old 07-17-19, 02:06 PM
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Air handler blower only comes on in emergency heat mode

I have carrier heat pump system model # FB4BNF050. The blower motor will only come on in emergency heat mode. Used to if it shut off you could give it a whack bottom right corner by the breakers and would come on! Now wont come on unless put it on emergency heat. Ideas please?
 
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Old 07-17-19, 03:05 PM
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Hi, it sounds like there is a loose connection, have you opened any covers to see what’s inside that bottom right side corner?
Geo
 
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Old 07-17-19, 03:13 PM
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That bottom corner is where the 2 50 amp breakers are. One of the lug screws was pretty rusty and I took the screw out and cleaned it up and wire looked like good connection.
 
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Old 07-18-19, 10:26 AM
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Does the thermostat have a fan ON function?
Geo
 
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Old 07-21-19, 09:51 PM
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I have seen these symptoms many times.
The control board is the most likely culprit.
The fan comes on with emergency heat because of the normally closed contact on the fan control board to the heat strip.

I usually just move a couple of wires on the fan control board to prove this and provide continuous blower operation until I pick up the control board.

Do you have one of these control boards?
 
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