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Hi, I have 50A65-120 board that's according to a technician, it's gone bad and need a replacement. Here's the exact board for reference:

My question is can I use 50A66-123 instead? Here's a link for reference. This one is also made by Lennox and has all the same connections but it's more than $100 cheaper.

My furnace model is 80UHG2-45A-3 and it only has blower fan active. Inducer motor kicks in and stops within a second and obviously no ignition. Tech ran some tests and concluded that board is gone bad.
 

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Yes that board should be compatible. Just pay attention closely when plugging in the wires as some locations may change. The white wires won’t really matter, you can plug them into any slot that says neutral. The black wire coming from the door switch is usually labeled “line” on the board and there should be another black wire coming from the transformer that usually plugs into a spot labeled “X-frmer” or something like that. The black wire from the blower goes to cool (if you have AC as well) and the red wire goes to heat usually. One thing that will probably change is the trouble indicator light will no longer match the key on the back of the furnace door. A new key should be included in the box with the new board tho so just slap that sticker over your old key.
 

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You normally have a set of 4 thermostat wires, red, yellow, green, and white. Red is power. White is heat. Yellow is AC. Green is blower. And then 2 more wires coming from the condenser (red and white). Those 2 wires just need to complete a circuit when the thermostat is calling for AC. So I do this by connecting the red wire to yellow (so it gets power when the thermostat calls for AC) and the white to common or ground (often marked with a “C” on the control board. Hope this helps!
BTW, I have a condensate pump with red and white wires coming out of it. Where do they go on controller board with rest of thermostat wiring?
 
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