Inside blower fan won't run

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  #1  
Old 05-31-18, 08:26 PM
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Inside blower fan won't run

My inside blower fan stopped working the other day. I noticed it was warm in the house, and when I checked the thermostat, saw that it was 78 when I had the AC set on 72. Checked the vents, no air coming out. Checked the outside AC unit, and saw that the line coming from the house was iced over. Immediately turned the AC off, and gave it time to thaw out overnight.

Started troubleshooting the next day. AC & heat are both working, but the fan will not turn on, whether the thermostat is set to heat, cool, or fan on, nothing turns it on. When I turn the fan on, I can hear it clicking like it's trying to kick on, but it doesn't do anything. Try manually spinning the fan, in case the capacitor is bad. Nothing. Capacitor looks normal, no swelling. Run an extension cord over and hook it up to the wires for the fan, and it immediately starts running, so the motor is working. My assumption at that point was that the control board was bad, so I order a new one.

New board arrived today, and after hooking it up, same thing. No fan. I'm out of ideas with my limited knowledge. Anyone have any suggestions of what else could be causing this problem, or what I can test to pinpoint the issue?
 
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Old 05-31-18, 11:08 PM
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Welcome to the forums.

Without a make and model or pictures...... we have no idea what you are working on.
We'd be guessing just like you are. How-to-insert-pictures
 
  #3  
Old 06-01-18, 07:50 AM
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Very good point, my apologies.

I have a Trane, model number 2TXCB036BC3HCAA. It is a gas furnace with A/C.

Here are two pictures of the different sections of the unit. In the bottom picture, you can see where I have temporarily hooked the extension cord up to the blower to get it to run so I can try to keep the house liveable while I try to figure this problem out.

I've done as much research online as I could, but I am far from an expert in anything related to this. I'm just hoping someone can point me in the right direction, with some suggestions on what else could be causing the problem, and how to test it to pinpoint the problem. I want to avoid just throwing parts at it until it works.
 
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Old 06-01-18, 08:08 AM
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That looks like the model number for the cooling coil. The furnace model number tag is inside on the side wall near the burner.

What is the part number on that control board ?
The blower is controlled directly from that board.
 
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Old 06-01-18, 08:30 AM
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Oh, my bad. The furnace model number is TUC1B080A9421AD.

The original control board was a 50A55-486. I replaced it with a 50M56U-843 (pictured), which according to the research I did is supposed to be a universal replacement part for the original board. However, replacing it solved nothing, as it is still doing the exact same thing.
 
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Old 06-01-18, 09:00 AM
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The replacement board you mention looks like 2 heating fan speeds. Doesn't look like that board in the picture.

You have a fan motor cooling terminal and an N connection on the board.
Had you tried setting the thermostat to FAN ON to see if fan worked ?
At the control board.... a jumper from R to G should also turn the fan on. Try that.
 
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Old 06-01-18, 09:14 AM
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The replacement board does have two heating fan speeds, hi and lo. The original board only had one. I hooked the wire that was connected to the heat on the old board (blue wire) to the hi heat on the new board. There is no wire going to the lo heat. I have two more wires coming from the blower that are both connected to 'Park' terminals. That's where they were on the old board. The black wire and white wires that I'm running to the extension cord currently are supposed to be on the COOL terminal (black) and one of the neutral terminals.

I have tried turning the fan on by itself. The only thing that happens is I hear a click from the blower area like it's trying to turn on, but nothing else happens. This is the same thing that happens if I try to jump the R & G on the control board.
 
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Old 06-02-18, 08:40 AM
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Anyone have any ideas on what components could keep the blower from running? In theory, it's not the control board, because I've replaced it, and have the same problem. It's not the blower itself, because it runs when I wire it directly to an extension cord. I assume it's not the capacitor, for the same reason. I'm out of ideas...
 
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Old 06-02-18, 09:33 AM
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It is the board or wiring to the board.

There are a row of N (neutral) tab connections.
There is a cool (hi) tab.

When you jumper R to G on the control board you should get 120vac between cool and N.
 
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Old 06-02-18, 10:01 AM
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I just did this, and the meter read 0, which seems to indicate a problem with the board... but what are the odds that the brand new board I bought would have the exact same problem as the old board?

I also tested the black wire going to the line tab, which is coming from the door switch, which I assume to be the 'master' power coming in to the board, and it read 116vac, so I know (I think) that power is coming to the board ok.

At this point, is my best bet to exchange this board as defective and try a new one?
 
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Old 06-02-18, 10:41 AM
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While you are at the board and it's powered...... do you hear a click when you jumper from R to G ?
 
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Old 06-02-18, 01:05 PM
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Yes, it definitely clicks when I jumper it or when I try to turn the fan on from the thermostat.
 
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Old 06-04-18, 01:14 PM
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So does it mean anything special that it is clicking when I jumper R to G at the board?
 
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Old 06-08-18, 11:00 AM
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I guess I'm going to just give up, and call someone to come look at it.

Thanks for trying to help me figure it out.
 
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