Bryant Central AC - indoor blower won't start, outdoor unit comes on fine

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Old 06-23-12, 07:45 PM
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Bryant Central AC - indoor blower won't start, outdoor unit comes on fine

System is about 8-10 years old. First time to use it this year, the air handler fan won't come on, and the outside unit works fine. The indoor air handler is in the attic. The thermostat is a battery digital setback type.
I've:
  1. Ensured the thermostat was set to a lower temperature so it will call for cool.
  2. Replaced the thermostat batteries.
  3. Ensured the cutoff switch near the air handler is on.
  4. Spun the blower squirrel cage fan by hand and it spins freely.
  5. Checked voltage coming in to the unit and it was > 200V.
  6. The motor does not hum or make any sound. (So not likely the hard start capacitor right?)
  7. Set the thermostat from fan to auto, no change.
  8. Checked the 5A fuse in the air handler. (more about that below)


There are three conductor thermostat wires going to the thermostat and the outside unit. Once set of wires has one wire turned back and wrapped around the insulation. It was my understanding that this set the two wires go to the outside unit, the set with using all three go to the thermostat. I think the two wires to the outside complete the thermostat circuit by going through high and low pressure switches.

I suspected that the low voltage wires to the outdoor unit could have been chewed through this winter by a squirrel in the chase where the run from the unit to the attic and I can't easily access that to check. I bypassed this outer circuit and connected the two thermostat wires together and it instantly blew the 5A fuse. (Oh [email protected], did I make things worse?). Then it dawned on me I could check for continuity on the two wires set and I have continuity. I also have continuity on a pair of wires going to the thermostat.

The HVAC company that installed the system is backed up for several weeks before they can send someone, and we have company coming. Looking for any and all suggestions and help
Thank you,
Paul
 
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Old 06-25-12, 02:30 PM
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Hi all,
It's supposed to be hot again later this week and our company arrives late tonight. Hoping someone has some advise for me I have the same airhandler downstairs and can switch out parts. I've have a ohm meter and can test voltages, but wasn't sure which wires should be what. I can also post a picture if that helps.
Thanks in advance!
Paul
 
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Old 06-25-12, 03:18 PM
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set the thermostat to system off and fan ON... Does the motor run? If no, jumper R to G at the thermostat terminals, does it run now?
 
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Old 06-25-12, 05:26 PM
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Sorry, which red/green

System turned off at the thermostat, fan set to auto, the fan does not start.

Sorry, which red/green?

I have two sets of thermostat wires with red/green/white One goes to the outside unit, the other the thermostat. Not sure which is which.

Set 1
Red <-> Red
Green <-> Grey
White <-> Green on second set of thermostat wires

Set 2
Red <-> Brown
Green <-> White from Set 1
White <-> Tied off, not connected

Yesterday I connected two wires and blew the 5 am fuse. I'm pretty sure it was Red and Brown but I'm not positive.

Thank you!
Paul
 
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Old 06-25-12, 05:37 PM
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Paul...did you turn the switch to Auto or ON? The test required it to be ON.
 
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Old 06-25-12, 05:45 PM
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Duh, it was set to ON not auto, sorry about that.
 
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Old 06-25-12, 06:24 PM
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I found the install manual

http://www.docs.hvacpartners.com/idc...im-fa4a-04.pdf

If I understand it correctly, the test will be to connect red and gray from the fan control together with unit off at thermostat and fan set to ON. Is that correct?
 
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Old 06-25-12, 06:53 PM
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still no go

I connected the Red and Grey wires for the fan speed control with the fan set to ON and system set to off. Fan motor did not move.
 
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Old 06-26-12, 02:48 AM
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Who said anything about red or green or gray? There are terminals designated R and G. You need to call a pro if you are unwilling to follow directions.
 
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Old 06-26-12, 09:17 AM
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My mistake, I see now you stated R G terminals. I was looking at wires, as the unit is mounted horizontally, on the floor to actually see the fan control board I need to lay down on the floor and look up at it. I connected the wires terminating at R and G and the fan did not spin or hum.
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When I get home tonight, I will disconnect any wires from R and G and jumper R and G.

What's next?
As far as calling in a professional, as I mentioned in my first post, I've called but they are scheduling two-three weeks out. I tried a second company yesterday, who services my oil burner, and they are backed up at least another week.

Thank you,
Paul
 
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Old 06-26-12, 11:04 AM
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If R to G does not work you need to check voltage to the motor while R is jumpered toG
 
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Old 06-26-12, 12:31 PM
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hvactecfw,

My wife just called to tell me it has started working. I had left it with the fan switch on the thermostat set to ON last night.
Would that indicate that the PCB board or the transformer might be flaky? Can I assume the fan motor is not likely the problem?
Thanks again for your assistance!!
Paul
 
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Old 06-26-12, 01:55 PM
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It would seem that way. If it happens again and while fan is set to on then check voltage between G and C at the control board while holding the door switch in.
 
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