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Old 04-06-2012, 06:42 AM   #1
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Thermostat Issue


OK, so I had a problem with my air handler (blower) not coming on when I started up my AC. The blower worked fine in the "heat" mode, would come on and blow fine. But when I switched to "cool" mode, the blower would not start. The AC condenser would start up and spin, but no air.

So, I had a tech come over, do a diagnosis, I thought it would be either a capacitor, fan motor or board, he diagnosed the board. After getting a $500 quote (on the board only mind you - not including the installation), I thought I could replace it myself. I called the local HVAC supply house and picked up a "replacement" board, not the original factory board, but one that "replaces" this unit. By the way the system is an eleven year old Bryant 80%.

I hooked everything up, and plugged it in, the fan started up immediately, but nothing at the thermostat, no readings, numbers - a blank screen. Since there was no problem with the thermostat before, and all I did was re-hook up everything, I am wondering whats up. Is there any fuse in the furnace that could have blown? It's hard to believe all of a sudden, I don't have power to the thermostat from the furnace. Ideas? Thanks in advance.

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Old 04-06-2012, 08:43 AM   #2
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Thermostat Issue


ok, just so I have this right... .

new board installed.

the condenser fan works,
the evap fan works.
The thermostat is a digital type and it does not work.

if thats the case, you have a wiring issue with the thermostat. The thermostat needs a hot wire and a neutral wire to power up. it sounds like you are missing one of them. I would suggest that you review your thermostat manual and the new control board manual and see if you have made a wiring mistake. I am assuming that you have a split system, so be aware that there are wires that thermostat control wires that run to each of these. There may be a broken wire someplace also.

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Old 04-06-2012, 09:13 AM   #3
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Thermostat Issue


are there batteries in the stat ?
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Old 04-06-2012, 09:25 AM   #4
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Thermostat Issue


new board installed. (Yes)

the condenser fan works, (It did before I installed the new board)
the evap fan works. (If you mean the fan inside the furnace (air handler), yes it comes on now)
The thermostat is a digital type and it does not work. (Yes, now it does not seem to have power - nothing lites up)

if thats the case, you have a wiring issue with the thermostat. The thermostat needs a hot wire and a neutral wire to power up. it sounds like you are missing one of them. I would suggest that you review your thermostat manual and the new control board manual and see if you have made a wiring mistake. I am assuming that you have a split system, so be aware that there are wires that thermostat control wires that run to each of these. There may be a broken wire someplace also. (I follow the logic, but all I did was disconnect the wires from the old board (wrote down exactly how they were connected), and re-connected them to the new board - same locations as on the old board.)
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Old 04-06-2012, 09:26 AM   #5
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Thermostat Issue


are there batteries in the stat ?(No, hardwired only)
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Old 04-06-2012, 09:32 AM   #6
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Thermostat Issue


Double check the connections on the board.
May not have good contact on a screw.
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Old 04-06-2012, 03:50 PM   #7
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Double check the connections on the board.
May not have good contact on a screw.
Thought about this also, but I have disconnected and reconnected the wires to the board several times and still no luck.
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Old 04-06-2012, 04:20 PM   #8
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Thermostat Issue


Put new board in,powered up and fan started immediately.
Is it possible the lead for the fan is actually for the stat? Stat has no power but the fan runs anyway.
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Old 04-06-2012, 06:16 PM   #9
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Thermostat Issue


Quote:
Originally Posted by sublime2 View Post
Put new board in,powered up and fan started immediately.
Is it possible the lead for the fan is actually for the stat? Stat has no power but the fan runs anyway.
Lets see, the blower lead (fan) is clearly different than any of the stat wires, much heavier with a clip end. In my original board it was actually connected to a "com" terminal, in the new board the instructions said to connect to a terminal labeled "blower".

My two sets of stat wires, one has (2) wires in it (White and red) the other has (5), blue, white, yellow, green and red. The hookup for the stat at the new board seems straightforward enough. Still confused, but thanks for the suggestions.
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Old 04-06-2012, 06:17 PM   #10
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Thermostat Issue


May be you should post what wires are connected where on the thermostat, and what wires are connected where on the control board.
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Old 04-06-2012, 10:17 PM   #11
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May be you should post what wires are connected where on the thermostat, and what wires are connected where on the control board.

As requested - thermostat is wired as follows: red wire - R terminal; yellow wire -Y/Y2 terminal; Green wire - G terminal; White wire - W/W1 terminal. New board is wired as follows: red wire - R terminal; red and yellow wires - Y terminal; green wire - G terminal; white wire - W terminal.
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Old 04-06-2012, 11:03 PM   #12
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Thermostat Issue


Quote:
Originally Posted by wherespete

As requested - thermostat is wired as follows: red wire - R terminal; yellow wire -Y/Y2 terminal; Green wire - G terminal; White wire - W/W1 terminal. New board is wired as follows: red wire - R terminal; red and yellow wires - Y terminal; green wire - G terminal; white wire - W terminal.
Where's the blue wire?
If its not hooked to the Rh or Rc of the stat you may need a jumper.
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Old 04-07-2012, 04:31 AM   #13
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Thermostat Issue


Quote:
Originally Posted by wherespete View Post

As requested - thermostat is wired as follows: red wire - R terminal; yellow wire -Y/Y2 terminal; Green wire - G terminal; White wire - W/W1 terminal. New board is wired as follows: red wire - R terminal; red and yellow wires - Y terminal; green wire - G terminal; white wire - W terminal.
There should be a wire from the A/C's condenser going to a C/common terminal on teh furnace board. An your stat probably needs a wire from the furnace boards C terminal to its C terminal.

Does your stat also have a RC terminal?
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Old 04-07-2012, 09:24 AM   #14
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Thermostat Issue


Pictures are worth a thousand words! So are model numbers.... equipment and stat...
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Old 04-07-2012, 09:26 AM   #15
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Thermostat Issue


My stat does not have a RC terminal. My stat has R, Y/Y2, G, C, W/W1. The new board has R, Y, G, Com 24 VAC and W. The old board had R, Y, G, Com 24VAC, W and HUM (which was not used). The old board was wired as follows - green wire - G terminal, red wire - R terminal, red and yellow wires - Y terminal, white wire - W terminal, and white and blue wires - Com terminal. All I did was duplicate the wiring layout from the old board to the new board. I never disconnected the wiring at the stat, did not see the reason to, it remains as it has been for 11 years.

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