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Old 06-22-2012, 08:31 AM   #1
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Central A/C Cooling


I have a Carrier HVAC system. The compressor condensor works on heat and cool. The air handler fan works sometimes. I tapped on the fan motor relay board- manager board and the fan starts sometimes.

I ordered a new fan manager board and installed it. The uiti ran perfectly for about thirty minutes and then shut off. The compressor condenser unit continued to work outside but the air handler fan went off. Where do you think the problem is? I'm an aerospace engineer and can trace most problems if some directions are given. Thanks.

Anna


Last edited by Anna64; 06-22-2012 at 08:35 AM. Reason: typos
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Old 06-22-2012, 08:47 AM   #2
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Quote:
Originally Posted by Anna64 View Post
I'm an aerospace engineer and can trace most problems if some directions are given.
Do you have the schematic for your unit?

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The compressor condenser unit continued to work outside
but the air handler fan went off. Where do you think the problem is?
What controls power to that motor?

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Old 06-22-2012, 09:07 AM   #3
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is there a door switch when going into the fan motor section? and jumping R to G right at the board should give you SUPPLY FAN ONLY...put stat if off on system fan in auto.do the jump at the furnace board if it works go up stairs and remove the stat and jump again R to G to see if the fan works on the jump....from the furnace board C and Y go out to the condenser for you to know when cooling calls.but check that door switch
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Old 06-22-2012, 09:09 AM   #4
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Yes, I have a schematic and it's powered by three phase 208/230 pull out circuit breaker at unit outside.

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Old 06-22-2012, 09:20 AM   #5
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There's no door switch. I jumped the relay switch with a jumper wire and the blower ran. I still replaced the fan motor relay board. It ran for about an hour and came to temperature set. The outside condenser still was running but the fan blower never came back on so as to blow more cool air as the temperature rose in the house.
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Old 06-22-2012, 09:27 AM   #6
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Just a non-pro WAG: intermittent open (heat induced) on the board connector or adjacent wiring.
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Old 06-22-2012, 09:42 AM   #7
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Not sure what you're stating here. The system is a heat pump and it works on the hot and cold side- no problems there.
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Old 06-22-2012, 09:47 AM   #8
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Here's what I would do:jump the relay, allow the blower to run constantly for a few hours. If within that time the blower motor overheats/shuts off than replace the motor.

is there a run cap on the motor? tried that?
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Old 06-22-2012, 09:50 AM   #9
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PLease explain the "run-cap" and it's function. I'll check for it. Why do you think it's the blower motor since is appears to run fine? Thanks- Anna
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Old 06-22-2012, 10:34 AM   #10
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Could be the capicitor on the blower motor or the control board on the condensor pump, right? What's the best way to verify corect operation of both? - Anna
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Old 06-22-2012, 04:33 PM   #11
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Come on anna it's not rocket science. Sorry couldn't resist

Get yourself a multimeter that does volts and amps. (ampsx2652)/volts= cap reading
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Old 06-22-2012, 05:11 PM   #12
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Quote:
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Come on anna it's not rocket science. Sorry couldn't resist

Get yourself a multimeter that does volts and amps. (ampsx2652)/volts= cap reading
Better you than me. My joke was not going be so pleasant.
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Old 06-23-2012, 12:04 AM   #13
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Ok giys, I'll check the cap readings tomorrow. What makes you think it's this rather than the fan blower board? Thanks.

Anna

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