Wiring a Lennox Thermostat Model 51M33

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Old 01-13-21, 09:40 PM
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Wiring a Lennox Thermostat Model 51M33

I want to re-install my old Lennox thermostat. It's a model 51M33. I have an electric AC. I don't know how the wiring was when it was on the wall. I have looked at some pictures online and saw at least two different versions
The letter shows the connector and the color the wire. No color means no wire connected to that connector.
1st version. O-Orange - B - R-Red - G-Green- Y1-Yellow - W1-White - L-Black - C-Blue - E Brown - T - T (no wires on the T connectors)
2nd version. O-Orange - B- R-Red - G-Green- Y1-Yellow - W1-White - L - C-Blue - E Brown - T-Brown - T-Black and then a white cable connecting W1 and E together.

I don't know which one to use. Help appreciated.

 
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Old 01-13-21, 09:55 PM
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Welcome to the forums.

You should have taken a picture of that old stat wired.
We could use a picture of your current stat wired.
Colors are not always followed and don't always mean the same thing.

This is what you should have.......
 
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Old 01-13-21, 10:00 PM
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Yes you are right. I should have taken a picture, Too late.
Yes , your picture shows the same I found online. That is the 2nd version that I typed above. So I do have to put a wire between W1 and E.And the black and brown go to the Ts.
Thank you very much
 
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Old 01-14-21, 10:16 AM
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Hi. Is it really necessary to put that white wire bridge between White and E connectors?
 
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Old 01-14-21, 10:32 AM
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The bridge between W and E allows the electric heat to work in emergency mode without the heat pump running.

You could also check the wiring connections at the air handler.
 

Last edited by PJmax; 01-14-21 at 12:08 PM. Reason: typo
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Old 01-14-21, 12:07 PM
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Thank you for your help.Will take that into account.
 
 

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