Lennox Circuit Board from 1991 Whisperheat.

Old 12-12-17, 05:10 PM
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Lennox Circuit Board from 1991 Whisperheat.

Hi all...

I want to install a Ecobee smart thermostat. My thermostat wiring is only 4 wires and I need to use the Power Extender Kit (PET) that came with it.

It instructs me to use the "C" connector on the furnace...but there is no C..just a W R Y T G

My question is...is the "T" the "C" connector?

Furnace is Old..I know...Will most likely need to be replaced in the next few years.....

Old 12-13-17, 08:53 PM
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Welcome to the forums.

No.... T is not usually a C. You can post the part number of the board for me or post a picture of the connection area. There should be a wiring diagram on the back of the blower door. A picture of that would be very helpful.
Old 12-19-17, 08:29 AM
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You need to get the heat exchanger inspected because it's most likely cracked. the heat exchangers in those furnaces are known on these boards to very consistently fail.

Forget about a fancy stat; replace that furnace, do not wait until it stops working or poisons you with co.

You don't want to have to make a snap decision.

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