# Problem with Lennox Pulse Furnace Wiring to Thermostat



## wirenut1110 (Apr 26, 2008)

I would guess "T" is the transformer common and if your new stat doesn't need it then cap it off.

If it is the common from the transformer, I'm surprised you didn't blow a fuse because it would create a dead short when it called for the fan or if there was enough resistance to prevent that, it may have pulled the voltage down.


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## qbert (Mar 23, 2009)

Trim your wires down alot of bare conductor showing. Disconnect the brn as stated. disconnect low volts at furnace and test xmfr you probably fried it


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## scalvin (Dec 28, 2009)

*Some Progress on Lennox Furnace Repair*

wirenut1110, you are right.

Tested the transformer and found no continuity on the load side. Replaced transformer and now have 24V to Terminal Strip. "T" does appear to be the transformer common. 

*However, when I removed "T" from the stat where it was connected on the stat to "G" along with "G" from the Terminal Strip, it created a dead fault. I isolated the dead fault and it is definitely coming from "T" when "T" is disconnected from the stat. However, the dead fault is corrected when "T" is reconnected to "G" on the stat..

The furnace now tries to fire but the fan or blower does not respond.

I can hear the spark from the spark plug firing and the sound of the heater trying to light, but the process keeps repeating without the furnace fully lighting while the fan/blower is not coming on.

I checked the schemtic on the furnace and it does indicate that "T" & "G" should be connected to "G" on the stat. Any ideas why the fan/blower now do not respond? It worked prior to me installing the new stat. I installed the old stat just to see if there was a compatibility issue, but the fan/blower is not working with the old stat either now.

Thanks for any help on this...



wirenut1110 said:


> I would guess "T" is the transformer common and if your new stat doesn't need it then cap it off.
> 
> If it is the common from the transformer, I'm surprised you didn't blow a fuse because it would create a dead short when it called for the fan or if there was enough resistance to prevent that, it may have pulled the voltage down.


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## scalvin (Dec 28, 2009)

*Some Progress on Lennox Furnace Repair*

qbert, you are also right.

Tested the transformer and found no continuity on the load side. Replaced transformer and now have 24V to Terminal Strip. "T" does appear to be the transformer common. 

*However, when I removed "T" from the stat where it was connected on the stat to "G" along with "G" from the Terminal Strip, it created a dead fault. I isolated the dead fault and it is definitely coming from "T" when "T" is disconnected from the stat. However, the dead fault is corrected when "T" is reconnected to "G" on the stat..

The furnace now tries to fire but the fan or blower does not respond.

I can hear the spark from the spark plug firing and the sound of the heater trying to light, but the process keeps repeating without the furnace fully lighting while the fan/blower is not coming on.

I checked the schemtic on the furnace and it does indicate that "T" & "G" should be connected to "G" on the stat. Any ideas why the fan/blower now do not respond? It worked prior to me installing the new stat. I installed the old stat just to see if there was a compatibility issue, but the fan/blower is not working with the old stat either now.

Thanks for any help on this...




;373126 said:


> Trim your wires down alot of bare conductor showing. Disconnect the brn as stated. disconnect low volts at furnace and test xmfr you probably fried it


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