Carrier AC Unit air handler blower does not run when AC is on

Old 05-11-14, 05:25 PM
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Carrier AC Unit air handler blower does not run when AC is on

Hello all,
I set the thermostat to "cool", set the temperature lower than ambient temperature. AC compressor and outside fan comes on BUT the indoor air handler blower does not.
While the AC compressor is running, I set the thermostat fan setting from Auto to ON and still nothing happens.
I shut off the AC by either increasing the temperature on the thermostat or switch it to off. THEN, if I set the blower to ON (instead of Auto) the air handler blower runs ok. At that moment, I set the AC back to cool and lower the temp and the air handler blower shuts off.
Looking into the furnace window, where the LED indicator is located, I see code 21 GAS HEATING LOCKOUT - Control will NOT auto reset. I'm not trying to run the heater but the AC.
I have a main power switch near the furnace so I shut off power for about 30 seconds. I re applied power, this time both the ac compressor AND the air handler blower came on! I thought my problem was solved (code 21 was still showing). Once the temperature reached the thermostat setting, the fan shut off (as it should) HOWEVER, the next time it tried to run the AC, the air handler blower didn't come on (outside compressor ran fine), so back to square one. I can reset the unit by killing power and I get a ONE time normal cycle.
I thought maybe the problem was on the thermostat so I bought a new one. Same results.
Not sure if having code 21 on the heater side causes the blower relay not to energize.
Any ideas? thanks for your help.
Old 05-11-14, 05:50 PM
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Hard to say without a make and model#.
Old 05-12-14, 01:38 AM
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Might be the smart intelligent effing board. Have you had bad storms in your area. If so I'd say faulty board. You know basic fan relay and switches worked to well to long. Industry can't make money if crap don't break so they came out with electronic digital technology. The slightest surge it's fried. Id bet a dime to a dozen donuts it's board issue.

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