Need Advice troubleshooting furnace blower problem

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Old 10-08-07, 09:08 PM
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Need Advice troubleshooting furnace blower problem

I need some advice in troubleshooting a problem with the blower in the furnace. The furnace is manufactured by Lennox, Model Number 80MGF4/5-100A-7, and the manufactured date on the panel is 1996. I am trying to troubleshoot why the furnace blower fails to operate in the cooling mode but the furnace blower will operate in the continuous fan mode. The unit will start normally and after running for approximately 4 to 5 hours, on Auto mode, the blower will stop running but the condensing unit will continue. The two LED lights will both have an 'alternating fast flash' and the service manual indicated a possible cause of improper ground to unit or line voltage below 75V. Sometimes the blower will cut on after 3 to 5 minutes after it stopped. I've checked that all of connections were intact. When the blower stops, you can heaa clicking noise in the furnace like an emergency blinker. Please advise.
 
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Old 10-09-07, 02:33 PM
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It may be the motor itself. On your system. it use the "heat" speed when you have fan "ON".

Take a meter and take a reading on the COOL tap where the fan motor goes to and check for power.. If you got power, then try changing fan speed..

If you are on black now (high), try the next speed down. (most of time it's yellow)
 
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