Furnace thermostat help!

Old 08-31-21, 11:59 AM
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Furnace thermostat help!

I am trying to install a smart thermostat and need some help.

I am replacing a Honeywell wireless system (not wifi) and have one question and one issue.

First off I was pulling the wires from the module in the basement and noticed that each color can allow 2 different wires to be put in. I saw that there were 2 wires going into the Y Terminal (see photo). When taking them off to add to the wifi system I combined the 2 together and added a 3rd wire that goes upstairs to the new thermostat. What is the second wire?

I now have everything hooked up and going (1 stage AC and heater only 2 years old). The ac works perfect and comes on without problems the heat is the problem.

When I turn the heat on the exhaust fan comes on like normal. I took the panel off and watched the process by the blower. After the fan comes on the igniter glows bright red for about 5 seconds then goes off with the flames never starting. A few seconds after the igniter goes our the blower comes on and it started blowing cold air in the house. Does anyone know what is going on? Please help!

I am using the thermostat and have the fossil model selected instead of the electric.
I am using the ADC-S3000 thermostat, lennox furnace (95%), everything is 2 ton.

I ran 5 new wires because I had the AC installed a few months ago and they put in the wireless model.

I have a C wire, R wire that is put into the RH terminal (per manual), W wire, 2 Y wires (one ran to the thermostat) and one G wire. I used the photo above to go directly from model to model.

Both ac and furnace have water pumps as well.


Last edited by PJmax; 08-31-21 at 07:51 PM. Reason: removed link
Old 08-31-21, 07:58 PM
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Welcome to the forums.

Please post actual wiring pictures.

You ran a five wire cable. That is borderline as you need a minimum of five wires for a basic system.
Rc, C, W, Y, G.
You should be removing the EIM module or at least disconnecting it.

Both ac and furnace have water pumps as well.
Do you mean condensate drain pumps ?
Those have no effect on the thermostat wiring unless you are connecting the safety overflow switches. If you are... let me know.

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